full rpt-2010 cvr - scripps institution of oceanographytigators in the earth section over...

U N I V E R S I T Y O F C A L I F O R N I A , S A N D I E G O

Earth Section

The Earth Section of the Scripps Institution of Oceanography

comprises the Geosciences Research Division (GRD) and the

Cecil H. and Ida M. Green Institute of Geophysics and

Planetary Physics (IGPP), which marked its 50th anniversary

this year. This report summarizes research conducted by inves-

tigators in the Earth Section over approximately the last aca-

demic year, with the goal of presenting a description of our

activities that is accessible to a broad audience.

Our work spans a broad range of subject matter in geology, geo-

physics, chemistry, biogeosciences, and climate science.

Observations, measurements, and collection of samples and data

are accomplished on global, regional, and local scales by exten-

sive shipboard and ground-based operations and also include

remote sensing by satellites and the use of wide-ranging instru-

ment networks. Extensive laboratory work often follows our

sampling programs, while theoretical developments and model-

ing play a strong role in data interpretation and guide the

design and implementation of experimental work.

Two new faculty members will join the Earth Section in

January: James Day is a geochemist whose research focuses on

planetary formation and evolution and Darcy Ogden who

applies computational fluid dynamics models to study explosive

volcanic eruptions. You may read further about their research

in their contributions to this report. Geoffrey Cook also joined

the Earth Section this year as a lecturer and will be teaching

several courses in our undergraduate earth science program.

Members of the Earth Section also received national recogni-

tion for their research, with Walter Munk receiving the

Crafoord Prize of the Royal Swedish Academy of Sciences and

Helen Fricker receiving the Martha T. Muse Prize for Science

and Policy in Antarctica.

Thanks to Robert Parker and Jennifer Matthews for their

efforts in compiling and producing this report. It is our hope

that you will find this a useful description of our ongoing

work.

Jeffrey Gee, current Head, Earth Section

Earth Section Annual Report

Duncan Agnew, Professor

Lihini Aluwihare, Associate Professor

Laurence Armi, Professor *

Gustaf Arrhenius, Research Professor †*

Luciana Astiz, Specialist *

Jeffrey Babcock, Associate Project Scientist *

George Backus, Professor Emeritus *

Jeffrey Bada, Research Professor †*

Katherine Barbeau, Associate Professor

Jonathan Berger, Research Scientist RTAD †

Wolfgang Berger, Research Professor †*

Donna Blackman, Research Scientist

Yehuda Bock, Research Scientist

Kevin Brown, Professor

Steven Cande, Professor

Paterno Castillo, Professor

C. David Chadwell, Research Scientist

Christopher Charles, Professor

Catherine Constable, Professor

Steven Constable, Professor

Geoffrey Cook, Lecturer *

Joseph Curray, Professor Emeritus *

J. Peter Davis, Specialist

James Day, Assistant Professor

Catherine deGroot-Hedlin, Associate

Research Scientist

Leroy Dorman, Research Professor †*

Neal Driscoll, Professor

Matthew Dzieciuch, Project Scientist

Peng Fang, Specialist *

Yuri Fialko, Professor

Robert Fisher, Research Scientist Emeritus *

Helen Fricker, Associate Professor

Edward Frieman, Professor Emeritus *

Jeffrey Gee, Professor

Freeman Gilbert, Professor Emeritus *

Peter Guenther, Specialist RTAD †*

Alistair Harding, Research Scientist

James Hawkins, Research Professor †*

Michael Hedlin, Research Scientist

David Hilton, Professor

Glenn Ierley, Professor

Miriam Kastner, Professor

Kerry Key, Assistant Research Scientist

Deborah Kilb, Associate Project Scientist

Devendra Lal, Professor

M. Gabriele Laske, Associate Research Scientist

Peter Lonsdale, Professor *

Guenter Lugmair, Research Scientist RTAD †

and Alex Shukolyukov, Project Scientist

Todd Martz, Assistant Professor

T. Guy Masters, Professor *

Stephen Miller, Specialist

Jean-Bernard Minster, Professor

Jens Mühle, Assistant Project Scientist *

Walter Munk, Research Professor †

Richard Norris, Professor

Darcy E. Ogden, Assistant Professor

John Orcutt, Professor *

Robert Parker, Research Professor †

Stephen Piper, Specialist *

David Sandwell, Professor

Annika Sanfilippo, Specialist RTAD †

John Sclater, Professor

Peter Shearer, Professor

Hubert Staudigel, Research Scientist

David Stegman, Assistant Professor

Lisa Tauxe, Professor

Michael Tryon, Assistant Project Scientist

Frank Vernon, Research Scientist

Martin Wahlen, Research Professor †*

Kristoffer Walker, Assistant Project Scientist

Bradley Werner, Professor

Edward Winterer, Research Professor †*

Peter Worcester, Research Scientist

Mark Zumberge, Research Scientist

* no annual report available† Research Professor and RTAD = retired with active research program

Image: Cretaceous Chalk cliffs at Tilleul Beach, Normandy, France. Geochemical studies of well pre-

served foraminifera in deep sea sediments indicate a brief glaciation during the otherwise warm green-

house climate when the chalk was forming about 90 Ma. Photo: Richard Norris.

Duncan Carr Agnew Frank K. WyattProfessor of Geophysics Principal Development EngineerEmail: [email protected] Email: [email protected]: x42590 Phone: x42411

Research Interests: Crustal deformation measurement and interpretation, Earth tides, SouthernCalifornia earthquakes.

Crustal Deformation (Strainmeters)

We continue to operate longbase laser strainmeters, six supported by the Plate BoundaryObservatory, and four others: an activity led by Wyatt and supported by staff members Don Elliottand Billy Hatfield.

Our most interesting results for the last year came from the El-Mayor/Cucupah (EMC)earthquake (magnitude 7.2), in the southern part of the Salton Trough on April 4, 2010 (day 94).The size of this event – the sixth largest earthquake in the last 100 years on the transform part ofthe Pacific/North-America plate boundary – and its proximity to three sets of strainmeters hasprovided the best records so far of immediate postseismic deformation.

Figure 1 shows the time series around the time of the event from the seven laser strain-meters installed around the Salton Trough: three at PFO, and two each at SCS and DHL. Allstrainmeters recorded through the mainshock, but the records do not give a coseismic offsetbecause the strains from the largest seismic wav es are large enough that the laser beam is nolonger pointed accurately at the far end; when this happens the interference pattern disappears andstrain is not measured. We do not have a reliable measure of strain for about 5 to 10 minutes; inthe plots we have set removed any across this gap. We do hav e reliable estimates of coseismicoffsets from the EW longbase tiltmeter at PFO, and from the more distant strainmeters in LosAngeles and Cholame.

After this interruption the strainmeters give a continuous record of even small deforma-tions. The plot shows data lowpassed (filter corner at 100 s) to remove the seismic coda. Theserecords show immediate, relatively smooth, strain changes at rates much higher than are observedat any other time. The data shown, and recorded later, suggest a more complex picture than sim-ple afterslip on the fault that caused the EMC earthquake. Afterslip on the part of the fault thathad the most coseismic slip (as determined by Prof. Yuri Fialko from InSAR and GPS data)would given the very small ratio of EW to NS strains observed at SCS. If that were the onlyprocess at work, we would expect all the other strainmeter records to look like scaled versions ofthe NS time series; that other records do not look like this implies that other sources of strain weretriggered by the mainshock.

Looking at the DHL data, we see a much larger and faster response on the NS, even thoughthe model predicts similar responses for the SCS and DHL NS strains. The ratio of EW to NSresponse is also larger than predicted by the model. And, we observe sev eral small steps in theDHL data that are not seen elsewhere. Our tentative explanation is that the DHL strainmeters aredetecting, not just strains from the EMC earthquake, but also strains from aseismic slip inducedon the San Andreas fault, which is only 1.5 km away at the closest. We hav e observed similarslip events on the DHL strainmeters, without accompanying seismic events, in 1997, 1999, 2003,2006, and 2008; the last was the largest episode of aseismic strain so far observed, and was alsorecorded on creepmeters operated across the San Andreas fault by Prof. Roger Bilham. The ideathat the post-EMC signals at DHL are caused by near-surface slip on the San Andreas fault is alsosupported by results from Prof. Bilham’s creepmeter array; the instrument at Salt Creek, 9 kmNW of DHL, showed a few mm of creep coincident with the EMC earthquake. Triggered surfacecreep has been observed before on the San Andreas and other faults of the Salton Trough.

-2-

Figure 1

Even more interesting are the signals from PFO, which is closest to the San Jacinto fault.All three strainmeters there start by showing postseismic strains that are roughly consistent, insize and shape, with the source being afterslip from the EMC fault: the signals are of the samesign, and larger on the NWSE and the EW than on the NS. Howev er, the strains over the firstmonth after this earthquake do not fit this pattern at all: instead, the NS and EW show trends ofabout the same size but opposite sign, while the NWSE shows less change; we also observe a sig-nificant change in trend on the long fluid tiltmeter. Slip on the San Jacinto fault would produceexactly this pattern: for example, the NWSE, being parallel to this fault, is the least sensitive toslip on it. Although the trends on the PFO instruments seem to be decreasing in rate, they aredoing so only with a long time constant; a similar pattern followed the 2005 Anza earthquake.These strains thus may indicate triggered deep slip on the San Jacinto fault.

Lihini I. Aluwihare

Associate Professor of Marine Chemistry

Email address: [email protected]

Phone extension: 2-4886

Research Interests: Carbon (C) and Nitrogen (N) Cycles of the upper ocean, isotopes (14C and 15N) and chemical composition as tracers of the biological and chemical history of organic matter in marine environments, microbial C and N metabolism in the deep ocean.

The research in our lab is currently focused on characterizing the journey of organic molecules from source to sink in aquatic environments. In particular, we are interested in the provenances of organic molecules accumulating in the aquatic environment, examining the biotic and abiotic transformations that classes of molecules undergo in these environments, and determining the residence time of molecules in various aquatic reservoirs. The ultimate goal of this research is to use organic molecules to (1) trace the exchange of carbon and nitrogen between earth’s major reservoirs of these elements and (2) identify mechanisms that lead to the ultimate preservation of organic matter in aquatic environments. In conducting this research we use a variety of analytical tools to characterize the chemical composition of molecules in aquatic environments; make stable and natural abundance radioactive isotope measurements to identify sources, transformations and residence time of organic molecules; and employ molecular biological techniques to examine the role of microorganisms in contributing and transforming carbon and nitrogen in these environments.

We have been involved in several projects examining carbon and nitrogen cycling in the eastern North Pacific Ocean. In collaboration with CalCOFI and the CC-LTER program we maintain a time series examining spatial and temporal variations in organic carbon and nitrogen in this region. We will use this data set to identify major processes controlling the inventory of the dissolved pools of these nutrients, and also to construct a carbon budget for the CalCOFI region. In addition, we are examining temporal and spatial variability in the radiocarbon content of various organic matter fractions in the eastern North Pacific Ocean to identify the timescales on which different classes of organic matter cycle. We are particularly interested in characterizing organic matter fractions that sustain upper ocean microbial production on short timescales, and also identifying chemical fractions that accumulate in the water column for millennia. Long-lived organic compounds represent a short circuit in the carbon cycle on ecologically relevant timescales. In an effort to understand the mechanisms contributing to organic matter accumulation in marine environments on long timescales we have begun to implement new chemical degradation and analytical methods to target highly oxidized (carboxylic acid-rich) molecules in marine organic matter. These studies will quantify highly oxidized compounds, identify possible sources through chemical characterization, and determine residence time through compound-specific radiocarbon measurements.

We have also begun to study organic matter cycling in terrestrial environments, and are examining the fate of terrestrial organic matter in marine environments. In the case of the former, we are investigating the cycling of organic carbon in Sierra Nevada lakes by comparing the composition and residence time of organic carbon in lakes that are influenced by different degrees of terrestrial input and have markedly different water residence times. The overall goal is to identify the timescales on which terrestrial versus aquatic production cycles in lakes. To examine the fate of terrestrial organic matter in marine environments we recently developed a compound-specific radiocarbon analysis method targeting molecules that serve as biomarkers for terrestrial organic matter (i.e., lignin oxidation

products). This method is currently being implemented to examine mechanisms of terrestrial organic carbon exchange between land and aquatic environments, and to establish the residence time of terrestrial organic matter in the open ocean.

Our lab is also involved in investigating carbon and nitrogen flow through microbial systems using specific lipid and genetic markers. We are continuing our work in the subsurface ocean, and have embarked on a collaboration to study the role of archaea in the carbon and nitrogen cycle of the Southern Ocean, where these organisms appear to be metabolically distinct from their pelagic counterparts in the North Pacific Ocean, for example.

Representative references:

Hansman, R. L; Griffin, S; Watson, J. T; Druffel, E. R. M; Ingalls, A. E; Pearson, A; Aluwihare, L.I. “The radiocarbon signature of microorganisms in the mesopelagic ocean.” PNAS 106(16) 2009, pp. 6513-6518.

Beaupre, S R and Aluwihare, L. I. Constraining the 2-component model of marine dissolved organic radiocarbon. Deep-Sea Research (II) 57(16) 2010, pp.1494-1503.

Kathy Barbeau

Associate Professor, Marine Chemistry


Phone extension: 24339

Research Interests: chemistry, biological availability and ecological effects of bioactive trace metals in the marine environment

We continue to investigate the biogeochemical cycling of trace metals in marine systems. Graduate student Kelly Roe is studying iron uptake and cycling by the nitrogen-fixing cyanobacterium Trichodesmium and representative strains of Trichodesmium-associated heterotrophic bacteria. Kelly’s studies this past year have focused on acquisition of heme as an iron source by a Trichodesmium-associated Roseobacter strain which we have in culture. The bacterium’s utilization of heme was explored with growth experiments on heme substrates, RT-QPCR gene expression analysis, and radioactive uptake. Undergraduate Ross Castillo joined the lab as a CCE-LTER Research Experiences for Undergraduates Fellow during the summer, and contributed his bioinformatics expertise to this project, as well as assisting in the development of quantitative PCR techniques to characterize the quantity and phylogeny of heme transport genes in natural marine bacterial assemblages. New graduate student Shane Hogle also joined the laboratory this summer and is gaining experience with bioinformatics and molecular biology techniques. Graduate student Randie Bundy participated in a research cruise in May 2010 in the California Current, led by Ken Bruland of UC Santa Cruz. Randie’s main activity on the cruise consisted of analyzing iron speciation via competitive ligand-exchange adsorptive cathodic stripping voltammetry (CLE-ACSV) in the surface and bottom boundary layer during a spring upwelling event. She is exploring the use of multiple analytical windows in CLE-ACSV analysis to extract additional information about the chemical nature of the iron ligand pool in natural samples.

A recent publication from our lab, authored by former post-doc Kristen Buck (Buck et al. 2010), demonstrates the utility of CLE-ACSV for mechanistic studies of trace metal speciation. In this study, the evolution of dissolved iron and copper speciation was followed through a simulated spring bloom event in a 15-day incubation experiment of natural seawater collected during austral winter from high- macronutrient, high-iron waters of the Bransfield Strait in the Southern Ocean. The experiment included unamended bottles as well as iron additions using the stable isotope of iron, 57Fe, as inorganic (57FeCl3) and siderophore-bound (57Fe-aerobactin, 57Fe-desferrioxamine B) amendments. Exposure to summer light conditions resulted in substantial growth for all treatments (Figure 1), mimicking the initiation of a spring bloom. The addition of iron resulted in a 30% increase in phytoplankton biomass over unamended controls by day 15, indicating that the unamended waters became iron limited despite initially elevated dissolved iron concentrations. Dissolved copper and copper speciation remained largely unchanged for all treatments of the incubation, with copper speciation dominated by exceedingly strong copper-binding ligands and low resultant free copper ion concentrations (10 16.3±0.3 mol L 1). A striking result of this experiment was the observation that strong iron-binding ligands were produced only in the unamended light bottles. This is some of the first published experimental evidence for the production of strong, specific iron binding ligands in situ in association with the development of iron limitation in a natural phytoplankton community, supporting the important role of biologically produced siderophore-type natural ligands in the marine iron cycle.

Figure 1. Example microscopy data from day 15 of the incubation in the Light +0 (Control, top left panel), +57FeCl3 (top right panel), +57Fe-desferrioxamine B (+FeDFB, bottom left panel) and +57Fe-aerobactin (+FeAero, bottom right panel) treatments. Slides were prepared from samples filtered onto 0.8 m black filters. Red color represents the natural fluorescence of chlorophyll and green color indicates protein (proflavin stain). Sample magnification is 400× for all figure panels, and the scale bar in the control panel is 40 m. From Buck et al. 2010.

Most Recent Publications

Dupont, C.L., K.N. Buck, B. Palenik and K. Barbeau. 2010. Nickel utilization in phytoplankton assemblages from contrasting oceanic regimes. Deep-Sea Res. I 57: 553-566.

Buck, K.N., K.E. Selph and K.A. Barbeau. 2010. Iron-binding ligand production and copper speciation in an incubation experiment of Antarctic Peninsula shelf waters from the Bransfield Strait, Southern Ocean. Mar. Chem. in press.

Jonathan Berger Research Geophysicist Email: [email protected] Phone: 42889

Research Interests: Global seismological observations, geophysical instrumentation, deep ocean observing platforms, global communications systems.

I have been working over the past few years on developing new sensors to replace the obsolete and no longer available STS1 and KS54000 sensors used in the Global Seismographic Network.

Progress on the interferometric seismometer developed by my colleague Mark Zumberge has reached a point where we are now funded by the US Geological Survey to deploy a 3-component borehole model at the Albuquerque Seismological Lab next year. We have worked for a couple of years on a vertical-component sensor, which now has nearly the required performance. But that model is not very suitable for borehole deployment. At the very least it would need to be scaled down in size and equipped with a leveling mechanism. So in collaboration with Erhard Wielandt we are experimenting with a new suspension with will not require leveling.

We have also developed a horizontal component seismometer that consists of a simple pendulum suspended by a monolithic, electrical discharge machined flexure. Three units have been built and tested with one now opening in a shallow borehole at PFO. The performance of this unit meets the GSN requirements.

I have also been working with John Orcutt and the OBSIP group at IGPP in developing a system that will allow us to deploy Seismological observatories in the deep ocean. Several years ago we proposed a large moored, floating platform to provide power and communications for a borehole seismometer (and many other instruments) on the ocean floor and in the water column. This was not funded, primarily due to its perceived cost. Still pursuing the goal of ocean floor seismic stations, we have recently teamed up with a small company, Liquid Robotics (http://www.liquidr.com/ ), which has developed a new device that may provide a breakthrough in deep ocean observations and telemetry.

The Wave Glider is a two-body sea-surface and underwater vehicle comprised of a submerged “glider” attached via a tether to a surface float. The system is propelled by the conversion of ocean wave energy into forward thrust, independent of wave direction. The wave energy propulsion mechanism is purely mechanical; no electrical power is generated. Just as an airplane’s forward motion through the air allows its wings to create an upward lifting force, the submerged glider’s vertical motion through the calm waters at the glider’s depth allows its wings to convert a portion of the upward motion into a forward force. As waves pass on the surface, the submerged glider acts a tug pulling the surface float along a desired course, controlled by a rudder on the glider. Separation of the glider from the float is a crucial aspect of the vehicle design. Figure 1 illustrates the principles of Wave Glider propulsion.

The basic idea is to use the Liquid Robotics technology to provide a surface platform to relay data acquired acoustically from an ocean bottom seismometer to the shore via satellite telemetry. The surface float is equipped with solar panels, an Iridium satellite telemetry modem/GPS and a small processor to provide commands to steer the system via a rudder on the glider. This control system can be used to steer the pair along a course, or to hold station in a very small watch circle. With support of the Green Foundation, we have conducted tests off the island of Hawaii in order to determine the power consumption of the bottom package when telemetering the required data flow from the seafloor to the Wave Glider. These test show that the average power to accomplish this is about the same as the power required by the SIO OBS package.

Our next step is to seek support to build a suitable OBS that would operate form 2+ years and conduct a realistic test in the deep ocean.

Relevant Publications

Mark Zumberge, Jonathan Berger, Jose Otero, and Erhard Wielandt., A Non-fedback Optical Seismometer. Bulletin of the Seismological Society of America, Vol. 100, No. 2, pp. 598–605.Zumberge, M. A., J. Berger, M. A. Dzieciuch, and R. L. Parker (2004). Resolving quadrature fringes in real time. Applied Optics, 43, 771-775.

Donna Blackman

Research Geophysicist



Research Interests: tectonic and magmatic processes that occur along plate boundaries, with emphasis on oceanic spreading centers; deformation of minerals and the development of seismic anisotropy during mantle flow.

Geophysical investigations of oceanic spreading center processes remain a main focus of my research. In 2009/2010 I continued with investigation of Atlantis Massif, an ocean core complex just west of the Mid-Atlantic Ridge axis, where detachment faulting has unroofed intrusive crustal rocks and at least lenses of mantle peridotite. New results this year were obtained through analysis of refraction data recorded by seafloor seismometers, in collaboration with John Collins at WHOI. The anomalous character of the massif’s central dome crust is clear compared to the neighboring rift valley and similar-age crust on the opposite ridge flank. The domal core has velocities >7.0 km/s at depths below ~2.5 km sub-seafloor, increasing to 7.5-7.8 km/s over the depth range 4.8-6.8 km. Within the core complex, the crust/mantle transition does not appear to be sharp as no PmP arrivals are observed. Within the axial valley, velocities do not reach mantle-transition zone values in the uppermost 6 km. We infer that crust is of normal thickness within the rift valley but that a somewhat thinner than average mafic section is present in the the central portion of Atlantis Massif. In the vicinity of Integrated Ocean Drilling Program (IODP) Hole U1309D, there is a constant velocity interval at 1-3 km depth with velocities of 6.6-6.8 km/s. The recovery of a dominantly gabbroic section from that 1.4 km deep hole and the extents of the relatively high and near-constant velocity region in our tomographic model suggest that this body of mafic intrusives extends a few km both laterally and vertically.

Figure. Velocity-depth profiles along refraction line across Atlantis Massif, spaced 1.5 km in portion of model where coverage is good. Intervals of 6-km length are color coded & line type varies west-east: solid, dash, dot-dash, & dotted. Preferred velocity model is shown below with velocity-depth profile intervals (color) marked at each western edge. Spreading axis is at x=12 km. Hole U1309D is near top of domal core, which is capped by detachment.

along refraction line acMassif, spaced 1.5 km model where coveraIntervals of 6-km lengcoded & line type varisolid, dash, dot-dashPreferred velocity modbelow with velocity-dintervals (color) markwestern edge. Spreadx=12 km. Hole U1309of domal core, which detachment.

I’ve also made some progress this year in modeling the development of mineral alignment during mantle flow, and associated seismic anisotropy. Working with Olivier Castelnau at University Paris, an ‘intermediate coupling’ case was completed. This incorporates rheologic anisotropy that is predicted for polycrystalline mineral aggregates that deform during viscous mantle flow beneath oceanic spreading centers. Our intermediate result indicates that proceeding with the ‘full coupling’ case is warranted– the change in flow velocities exceeds 20% of the plate spreading rate (a relevant metric) in some portions of the field when first-past anisotropic rheology is included in the stiffness matrix for the flow solution. This is not negligible. However, potential feedbacks need to be assessed. In the coming year, we will develop an iterative procedure that can provide the fully-coupled solution.

Planning for potential future projects where ocean drilling is a major component took a significant portion of my broader efforts. The current IODP will finish in 2013 but recent deep drilling and borehole technology appears poised to open some new opportunities for studying the structure and processes that characterize the ‘basement’ portions of oceanic lithosphere. In particular, there is significant momentum toward pursuing full penetration of a complete crustal section and recovery from well into the uppermost mantle (several hundred meters), as part of a new, post-2013 program. If this project goes forward as envisioned, there would be a number of valuable geophysical studies that could be conducted for the first time, with sensors deep within the ocean crust and upper mantle. So, for this reason, I have participated in several workshops where scientists/engineers have advanced the general plan and begun to lay groundwork for specific milestones along what would be a long-term effort.

Finally, a brief look at spreading center structure approaching the Chile Triple Junction, where the rift is subducting beneath the South American continent, was obtained during a brief research cruise. Graduate student Ashlee Henig (whose main research topic is seismic tomography at Atlantis Massif) and I joined a dominantly biological investigation of deep-sea vent ecosystems. Our contribution was to provide seafloor mapping expertise so that video and dredge targets could be identified. The ship left Chile just a couple days before the magnitude 8.8 Maule earthquake occurred, so we had first-hand views of some of the damage in Santiago when we came into port ~3 weeks later.

Blackman, D.K., and J.A. Collins, Lower crustal variability and crust/mantle transition at the Atlantis massif oceanic core complex, accepted w/minor revision in September, Geophys. Res. Lett. 2010.

Harmon, N. and D.K. Blackman, Effects of plate boundary geometry and kinematics on mantle melting beneath the back-arc spreading centers along the Lau Basin, Earth Planet. Sci. Lett. (2010, in press), doi:10.1016/j.epsl.2010.08.004.

N. W. Hayman, W. Bach, D. Blackman, G. L. Christeson, K. Edwards, R. Haymon, B. Ildefonse, M. Schulte, D. Teagle, andS. White , Future Scientific Drilling of Oceanic Crust , Eos Trans. AGU 91, #15, 2010. p133-134.

Figure 1. Displacement vs. epicentral distance for the 2010 El Mayor-Cucapah earthquake showing S-wave propagation across the California Real Time Network (CRTN) stations in southern California. The displacement waveforms are available in SAC format from SCEDC (http://www.data.scec.org/research/MayorCucapah20100404/).

Yehuda Bock Research Geodesist and Senior Lecturer Email address: [email protected]; Cell: (858) 245-9518 Research Interests: Space geodesy, crustal deformation, early warning systems for natural hazards, GPS seismology, GPS meteorology, GIS and Information Technology

Highlights of Yehuda Bock’s research in 2010 with graduate students Brendan Crowell and Diego Melgar, SOPAC staff, and collaborators at IGPP and Caltech, include studies of transient deformation in the Salton trough, and real-time observation and modeling of the Mw 7.2 April 4, 2010 El Mayor-Cucapah earthquake. We continued to expand the California Real Time Network (CRTN - http://sopac.ucsd.edu/projects/realtime/), now numbering more than 160 continuous GPS stations. The El Mayor-Cucapah earthquake demonstrated convincingly the power of dense near-source, high-rate, real-time GPS networks for earthquake early warning [Crowell et al.,2009] and rapid earthquake response. A robust set of 1 Hz data was collected from over 100 CRTN stations in with a latency of about 0.4 seconds, and inverted to provide on-the-fly total displacement waveforms, which captured the propagation of the S-wave through the southern California crust at stations up to 450 km from the epicenter (Figure 1). By “total displacement” we mean direct measurement of both static and dynamic displacements, previously relegated separately to geodesy and seismology, respectively. While most broadband seismic stations clipped for this earthquake (although accelerometers at the same sites did not), the real-time GPS stations did not saturate and continued to provide on-scale data. We applied a multi-rate Kalman filter to optimally combine data collected by 100 Hz strong motion instruments at local seismic stations and 1 Hz GPS data from CRTN to obtain 100 Hz total displacement waveforms at co-located stations as far as 300 km from the earthquake’s epicenter (Figure 2). Displacement waveforms in seismology are traditionally obtained by integration, polynomial fitting and filtering of strong motion records. The displacements so obtained are band-limited since the low frequency components (including the static deformation) are not accurately determined. Our Kalman filter approach does not have these limitations, and is well suited for large dense GPS/seismic networks and real-time processing [Bock et al., 2010].

Figure 2. Displacement waveforms for the 2010 El Mayor-Cucapah earthquake obtained by applying a multi-rate Kalman filter to co-located 100 Hz strong motion and 1 Hz GPS stations.

We have also been investigating a strain transient centered on the Obsidian Buttes fault just south of the Salton Sea detected from analysis of a long-history of survey-mode GPS measurements taken over the last 25+ years. Using interpolated site velocities over a 0.01 degree grid for field survey data collected before and after 2001 followed by 2-D strain analysis, suggests accelerated slip on the Obsidian Buttes fault between 2001 and 2009, equivalent to a magnitude 5.3 earthquake. The associated strain transient has caused an accelerated fault parallel slip rate deficit of 5-7 mm/yr along the southern San Andreas fault near Bombay Beach, corresponding to a Coulomb stress increase since 2001 of ~0.5 MPa centered along the 2009 Bombay Beach seismic swarm (Figure 3). The ongoing strain transient is loading up the transtensional faults in the Salton Sea and the southern San Andreas fault, presumably reducing the time to its expected rupture [Crowell et al., 2010].

Recent Publications and Presentations Bock, Y., R. Clayton, B. Crowell, S. Kedar, D. Melgar, M. Squibb, F. Webb, E. Yu, Earthquake Early Warning in

Southern California Using Real Time GPS and Accelerometer Data: Lessons from the Mw 7.2 2010 El Mayor-Cucapah Earthquake (2010), Poster at SCEC Annual Meeting, Palm Springs, September 12-15, 2010.

Crowell, B., Y. Bock, and M. Squibb (2009), Demonstration of earthquake early warning using total displacement waveforms from real time GPS networks, Seismo. Res. Lett., 80(5), 772-782, doi: 10.1785/gssrl.80.5.772.

Crowell, B. W., Y. Bock, D. Sandwell, and Y. Fialko (2010), Accelerated loading of the San Andreas fault by transient deformation in the Salton Trough, Nature Geoscience, resubmitted after review.

Figure 3. Coulomb stress change associated with slip on the Obsidian Buttes fault for (a) vertically oriented right-lateral faults at N45ºW; (b) N15ºE; and (c) vertically oriented left-lateral faults at N56ºE strike angles, using an effective friction coefficient = 0.4. The focal mechanism of the largest event, Mw 4.8 on March 24, 2009, during the 2009 Bombay Beach seismic swarm is shown in (c) and the location of the Bombay Beach Seismic Swarm are the black dots. The white dots are recent seismicity since the 2005 Obsidian Buttes seismic swarm from the SCEC data archive except the Bombay Beach seismic swarm.

Kevin Brown

Professor



Research interests: Rock mechanics laboratory experiments, high-speed friction and direct shear experiments, physical properties. Theoretical developments in earthquake physics relating changes in fault rheology during the earthquake cycle and the onset of unstable slip (origins of slow and fast earthquakes etc.). Long-term ocean observatory developments. Combining offshore geodetics and physical oceanography to facilitate enhanced integrated cross-disciplinary marine science. Marine hydrological/geochemical instrumentation development to study the interactions between hydrology/gas hydrates/active tectonic and aqueous geochemical variations.

In the last few years my previous work on faults and fluids and earthquakes has led two separate but ultimately related areas of research. 1) Marine engineering and deep sea submersible studies where I have tended to specialize in the development hydrologic instrumentation and very lately a geodetic observatories for the study of how fluids interact with active tectonic systems in the marine environment. These studies are now increasingly being focused on dynamic properties of fault motion and earthquakes. To this end I am currently conducting the following two projects: 1) An experimental/theoretical study into the physics of earthquakes and, 2) A new study focusing on the surface deformation associated with the El Mayor-Cucapah, 04 April 2010, 7.3 Earthquake.

Earthquake Fault Physics

I am concentrating my research focus on experimental and theoretical studies of the low and high speed (up to 1-2m/s) frictional of properties of fault zones to come at the “earthquake physics and fault stability problem” from that direction. This work is being conducted with Yuri Fialko and Erica Mitchell (my graduate student) based at IGPP and I have found this direction to be both pleasant and fruitful. Recent results indicate the physics involves the underlying intimate coupling between the complex dynamic processes involved in sick-slip behavior itself and the rheology of the gouges under different environmental conditions (such as temperature, normal stress, and system compliance).

High-speed weakening processes directly bear on earthquake propagation physics and the origin of the anomalously low state of resolved shear stress on many major plate boundary faults systems, hazardous long-run-out landslides, and the motion on misaligned faults, and low angle detachments. In addition to experimental work my laboratory is becoming familiar with complex numerical simulation packages such as ABACUS. This package is fully coupled and can undertake a wide variety of simulations both hydrologic and poro-elastic modeling of the well responses in terms of tilt, pore pressure etc. We are developing in conjunction with Yuri a non-linear model and supporting experimental evidence that explains the principal properties of an initial high velocity weakening phase during earthquake initiation in terms of a thermally controlled increase in the plasticity and decrease in yield strength of the contacting asperities in response to frictional heating. It relies on the well understood concepts of rock plasticity at elevated temperatures and stresses and accounts for the weakening we observe in high speed friction tests by considering both the Wachtman-Anderson relationship for the linear temperature dependent decrease of the elastic modulus and the hyperbolic sine creep law to account for greatly increasing creep rates at elevated contact stresses as local asperity temperatures rise above ~500-700°C. Our latest results, however, indicate that our and existing high-speed data may have additional strongly non-linear dynamic aspects build into it resulting from “block and slider type” high frequency chatter (frequencies of >100 Hz to 1000? Hz at seismic slip-speeds). The net result is that near instantaneous slip-speeds on the actual slip surface may vary considerably from the imposed average

Complex patterns of sand blow activity, 2.5m spot data. Roads and houses for scale.

driving velocity by as much as an order of magnitude or more. This results in the imposition of a high frequency/energy component that leads to more effective weakening of the rock surface (i.e. for a given imposed exterior average velocity the local high frequency/velocity component leads to greater than expected dynamic weakening). I have currently redeveloped the high-speed shear system (three different versions so far) so we can evaluate the degree of high speed weakening on a slip surface both with and without the high-frequency chatter component.

The redevelopment has just succeeded and the results are different from what has been published over the last 10 years (the new work is being written up). This has led to both some “consternation” in the experimental community and the beginnings of a re-evaluation of the very nature of high speed weakening processes in shear zones. While the “experimentally generated high-frequency chatter” is a complex product of the dynamic weakening on the shear surface and “instrument effects” (relating to the instrument’s stiffness and inertial dampening), very similar things are to be expected in natural faults. These have both scale dependent stiffness and inertial terms. The larger question then becomes, when a natural fault slips during an earthquake is the dynamic weakening term also substantially dictated by a hidden “high-frequency, high

While theory and experiment can start to open us up to questions surrounding the controls on dynamic fault strength the question remains can we actually observe such high-frequency processes in nature. The potential or probable existence of a high frequency “earth-chatter term“ should be a prime target for future research. My interests have thus evolved to include potential future observations of such high frequency terms. They have been measured in just few studies to date so the field is “wide open”. Due to differential attenuation effects during the propagation of seismic energy through the earth, the high frequency terms should be effectively filtered out after relatively short propagation distances (either in fault damage zones or in near surface sediments). Thus, it would seem that a deep observatory with near field acoustic sensors and accelerometers place across the fault itself may be the only way to capture this hidden high frequency component to the energy balance of earthquake rupture propagation.

Liquefaction Associated with the 7.2 El Mayor-Cucapah, 04 April 2010 Earthquake

The Colorado delta region lies above the southern portion of El Mayor-Cucapah Earthquake, a 120 km long oblique right-lateral transtensional rupture that terminates near the Gulf of California. The intent of the work is to undertake a basic systematic mapping of the surface liquefaction and associated faulting occurring in the several 100km square delta region of the Colorado River. The work will form part of a graduate student thesis for Erica Mitchell. Deformation in the delta is extremely widespread and complex. The mapping will be undertaken primarily utilizing geo-referenced satellite images followed by field checking. This work has just been initiated.

Steven Cande

Professor



Research Interests: Global plate reorganizations, tectonic evolution of the Pacific and Indian Oceans, motion between East and West Antarctica, tectonics of the Western Ross Sea, source of marine magnetic anomalies, geomagnetic polarity timescale, paleo-intensity variations of the geomagnetic field.

A large portion of my research over the last 10 years has focused on the tectonics of the ocean floor in the region in the far south Pacific and Indian Oceans near Antarctica. By studying the magnetic anomalies, fracture zones and other structural features in the region north of the Western Ross Sea we have been able to piece together a record of the motion between East and West Antarctica that took place in the mid-Cenozoic (between roughly 45 and 25 Ma). This record is very important for studies of global plate motions as well as for regional studies of Antarctica, such as determining when there was uplift of the Transantarctic Mountains (a factor in studies of paleo-climate). In 2007, in conjunction with SIO grad student Roi Granot and colleagues from Caltech and New Zealand, we carried out a detailed seismic survey on board the NSF Icebreaker Nathaniel Palmer of the Adare Basin, the area of the seafloor east of Cape Adare, Antarctica, which contains the best marine tectonic record of the motion between East and West Antarctica (Figure 1). This history is recorded in the complex structures observed in the sedimentary sequences above the seafloor.

Figure 1. Topographic map of the Ross Sea region of Antarctica. The inset map shows the structures and magnetic anomalies of the Adare Basin, east of Cape Adare. A detailed seismic survey was carried out in this basin on board the R/VIB Nathaniel Palmer in 2007. From Granot et al. (2010).

Of particular interest to us was any evidence for motion which took place after the main episode of seafloor spreading ended around 25 Ma ago. This “post-spreading” extension is of interest because it is a record of the plate motions which have been controlling the tectonics of the area for the most recent period of time. The seismic data (Figure 2) revealed that there was one particularly large episode of post-spreading rifting which took place around 15 Ma. This rifting episode involved about 5 to 10 kms of extension and caused renewed uplift of the flanks of the Adare Trough and faulting throughout the central and west side of the basin. Examples of these structures are shown in Figure 2.

Figure 2. Example of the multi-channel seismic data collected in the Adare Basin. The pattern of faulting revealed an episode of “post-spreading” extension which took place around 15 Ma. From Granot et al. (2010).

Recent Publications:

Granot, R., S.C. Cande, and J.S. Gee, 2009. The implications of long-lived asymmetry of remanent magnetization across North Pacific fracture zones, Earth Planet. Sci. Letts., 288, 551-563,

Granot, R., S.C. Cande, J.M. Stock, F.J. Davey and R.W. Clayton, 2010. Postspreading rifting in the Adare Basin, Antarctica: Regional tectonic consequences, Geochem. Geophys. Geosys.,11, Q0805.

Cande, S.C., P. Patriat and J. Dyment, 2010, Motion between the Indian, Antarctic and African plates in the early Cenozoic, Geophys. J. Int., 183, 127-149

Croon, M.B., S.C. Cande and J.M. Stock, in press. Abyssal Hill Deflections at Pacific-Antarctic Ridge-Transform Intersections, Geochem. Geophys. Geosys.

Pat Castillo

Professor of Geology



Research Interests: geochemistry and petrogenesis of magmas produced within and along divergent and convergent margins of tectonic plates; magmatic and tectonic evolution of continental margins; mantle geodynamics

My recent research activities focus on the origin of oceanic intraplate magmatism, specifically, the origin of ocean island basalts (OIB) that form linear volcanic island chains and aseismic ridges. A widely accepted explanation for these volcanic features is the hotspot or plume hypothesis, which calls for the occurrence of fixed, hot, upwelling plumes consisting of primitive and recycled Earth materials from the lower mantle; these stationary plumes generate and deposit OIB on the surface of moving oceanic plates. Although the hotspot hypothesis has remained popular for more than four decades, continuous accrual of data shows difficulties in reconciling the observables with the presence of deep and/or primitive mantle reservoir for the source of OIB. The main alternative hypothesis is the plate stress hypothesis, which calls for the origin of linear volcanic island chains and aseismic ridges through lithospheric rupturing processes. In this scenario, the upper mantle consists of a ubiquitous though random mixture of small to moderate scale (1–100 km) enriched, crustal lithologies embedded in a depleted mantle matrix; such enriched lithologies are injected into the upper mantle through plate subduction.

To verify whether lithospheric rupturing processes can generate OIB or not, my colleagues and I analyzed lavas from non-linear oceanic volcanoes such as seamounts near the East Pacific Rise and ridges along fossil spreading centers. These volcanoes form along lithospheric ruptures and generate lavas that are very similar to those that form linear volcanic chains (i.e., OIB-like). In other words, the bulk of the lavas are alkalic and geochemically more enriched in incompatible trace elements and radiogenic isotopes than normal mid-ocean ridge basalts (MORB). For the near-ridge seamount investigation, our specific objectives were to constrain the source of near-ridge seamount lavas and if these lavas contain 3He/4He ratios higher than those of normal MORB; high 3He/4He ratios are a hallmark feature of OIB from prominent linear volcanic chains such as Hawaii, Galapagos, Samoa, and Iceland. Our results show that the source of OIB-like seamount lavas is indeed the heterogeneous upper mantle, similar to that proposed for the source of OIB by the plate stress hypothesis. However, the lavas do not have high 3He/4He ratios. Thus, the high 3He/4He of OIB cannot be simply coming from dispersed, heterogeneous lithologies in the upper mantle; the mantle source of high 3He/4He OIB is unique to linear volcanic chains and likely resides in the deeper mantle.

Results of our investigation of the OIB-like lavas from fossil spreading centers in the eastern Pacific show that the lavas also originate from the heterogeneous upper mantle. This is again consistent with to the proposed source of OIB by the plate stress hypothesis. However, results also show that, together with petrologic and geochemical data for near-ridge seamounts, intraplate volcanoes that do not form linear volcanic chains in the eastern Pacific define a compositional continuum ranging from normal MORB-like to OIB-like. The data indicated to us that the entire compositional spectrum of these intraplate lavas in the eastern Pacific results from variations in the degree of partial melting of a common, compositionally heterogeneous mantle source consisting of

more easily melted, geochemically enriched components of varying sizes and amounts embedded in a depleted lherzolitic matrix. Large degree and more voluminous partial melting produces normal-MORB-like melts represented by some near-ridge seamount lavas whereas small degree produces OIB-like lavas represented by some fossil spreading center lavas. This is very similar to the main idea of the plate stress hypothesis for generating OIB that form linear volcanic chains. However, similar to the results of our near-ridge seamount study, our new fossil spreading center data suggest that the source of OIB that form linear volcanic island chains and aseismic ridges is unique and likely resides in the deeper mantle.

Recent publications:

Tian, L., Castillo, P.R., Lonsdale, P.F., Hahm, D., and Hilton, D.R., “Petrology and Sr-Nd-Pb-He isotope geochemistry of post-spreading lavas on fossil spreading axes off Baja California Sur, Mexico”, Geochem. Geophys. Geosystems, submitted.

Castillo, P.R., Clague, D.A., Davis, A.S., and Lonsdale, P.F., “Petrogenesis of Davidson Seamount lavas and its implications for fossil spreading center and intraplate magmatism in the eastern Pacific”, Geochem. Geophys. Geosystems, 11, Q02005, doi: 10.1029/2009GC002992, 2010.

Macpherson, C.G., Chiang, K.K., Hall, R., Nowell, G.M., Castillo, P.R., and Thirwall, M.F., “Subduction related magmatism in the absence of a slab-derived flux: Evidence from high-Nb basalt magmatism, Semporna peninsula, SE Sabah, Borneo”, Journal of Volcanology and Geothermal Research 190, 25–38, 2010.

Hahm, D., Castillo, P.R. and Hilton, D.R., “A deep mantle source for high 3He/4He ocean island basalts (OIB) inferred from Pacific near-ridge seamount lavas”, Geophysical Research Letters, 36, L20316, doi:10.1029/2009GL040560, 2009.

Clague, D.A., Paduan, J.B., Duncan, R.A., Huard, J.J., Davis, A.S., Castillo, P.R., Lonsdale, P.F., and DeVogelaere, A., “Five Million Years of compositionally-diverse, episodic volcanism; construction of Davidson Seamount atop an abandoned spreading center”, Geochem. Geophys. Geosystems, 10, Q12009, doi:10.1029/2009GC002665, 2009.

C. David Chadwell



Phone extension: x42663

Research Interests: Seafloor tectonics of subduction, transform motion, and seafloor spreading. Volcanic collapse, slope stability and associated geo-hazards. Seafloor geodetic techniques with acoustics and GPS.

The past year we published results from a two-year effort to monitor for motion across an incipient crack on the seafloor slope of the Gaviota slide in the Santa Barbara Basin (Blum, et al., 2010). To do this, we developed a new acoustic ranging system moored above the sea floor that interrogated daily seafloor transponders which straddled the crack. Across this nearly 1 km baseline, we measured no motion exceeding ± 7 mm/yr with a 99% confidence level. Additionally, a CHIRP sub-bottom profile across the crack revealed no evidence of downslope creep. We concluded that there is no active creep and that the cracked formed concomitantly with the Gaviota slide.

Work also progressed on the development of new observational platforms and new modeling approaches. At the Fall 2009 AGU, I reported the initial success of a new moored buoy system (developed with SIO colleagues, Brown, Tryon, and Send) for combining GPS and acoustics to measure the position of seafloor transponders once per minute continuously (Chadwell et al, 2009). Extensive testing was conducted over the summer and the buoy was deployed in Sept. 2010 in 1200-m deep waters for a several month long deep water test. On the modeling effort, I published analysis (with A. Sweeney) determining the appropriate ray trace equations for acoustic travel time measurements consistent with millimeter-level seafloor geodesy (Chadwell and Sweeney, 2010).

Finally, I organized and led (with P. Lonsdale) a NSF sponsored Rapid Response Cruise to Chile following the 2010 earthquake, to resurvey with the seafloor slope of the rupture area using multibeam bathymetry. German researchers had mapped the region prior to the earthquake and we collaborated on differencing the two data sets. No large slides were found, suggesting that tsunami observed along the Chilean coast several hours after the main event were due to hydro-dynamical interactions and not to a delayed slumping of the slope. Investigation continues at this time looking for more subtle evidence of slope changes.


Chadwell, C.D., Brown, K. M., Tryon, M. D. and U. Send (2009), Seafloor horizontal positioning from a continuously operating buoy-based GPS-acoustic array, Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract G22A-01.

Blum J. A., Chadwell, C. D., Driscoll, N. and M. A. Zumberge (2010) Assessing slope stability in the Santa Barbara Basin, California, using seafloor geodesy and CHRIP seismic data, Geophys. Res. Lett., 37, L13308,doi:10.1029/2010GL043293.

Chadwell, C. D. and A. D. Sweeney (2010), Acoustic Ray-Trace Equations for Seafloor Geodesy, Marine Geodesy, 33, 164-186.

Chadwell, C.D., Lonsdale, P., Weinrebe, W., Diaz- Naveas, J., Contardo, X., Contreras-Reyes, E., Henig, A., Kluesner, J., Moscoso, E., Barroso, E., Sasagawa, G., Sweeney, A., Tryon, M., and M. Viel-Gonzalez, (2010), Offshore Investigations of the 27 Feb. 2010 Maule, Chile earthquake rupture, AGU Chapman Conf., Great Earthquakes and their tsunamis, Vina del Mar, Chile, 16-24 May 2010, Abstract 18A-4.

Figure 1: Bathymetry collected during the rapid response cruise. Four pressure sensors were deployed three weeks after the event with the possibility of detecting large > 10 cm post event motions. They record the ambient seawater pressure at the seafloor every minute for up to 12 months and will be recovered in March 2011.

Christopher Charles

Professor of Oceanography



Research Interests: Reconstruction of climate variability on interannual to ice age timescales, isotopic tracers of ocean/atmosphere variability, low temperature geochemistry

The work in my research group involves the reconstruction of ocean and climate variability using geological archives such as corals or deep sea sediments. Areas of emphasis in 2010 included work on a collection of fossil corals from the Line Islands (Central Pacific) that, we hope, will yield as yet the most detailed record of the El Niño/Southern Oscillation (ENSO) phenomenon over the last 7,000 years. The goal of the work is to determine whether ENSO was sensitive to the known changes in solar radiation over this 7,000 year interval, and, by inference, to what extent it is sensitive to any perturbations in radiation—including the forcing from increased greenhouse gases. This work is being done in collaboration with former SIO student Kim Cobb and is being carried out by visiting SIO student Niko Westphal.

Another continuing theme for the group is the role of deep ocean ventilation over ice age cycles. Currently, we are making use of a collection of deep sea sediment cores collected on the Namibian margin to understand the how the distribution of various tracers that should be transported by ocean currents may have changed over the course of the last full ice age cycle (150,000 years). This work is being done in collaboration with Niall Slowey at Texas A+M, and the first phase involved extensive radiocarbon measurements carried out by former SIO student Jenna Munson. The next (current) phase involves analysis of the ostensibly conservative tracers captured in the “depth transect” of sediment cores, work to be done by current student Alan Foreman.

Other graduate student activities in the group involved analysis of radiocarbon variaibility in the Santa Barbara Basin over the last 200 years (Lydia Roach); generation of a new record of hydroclimate variability in the eastern Sierra Nevada, covering the last millennium, using the deuterium content of lake sediment fatty acids (Lydia Roach); work on the nitrogen isotopic composition of equatorial Pacific water and bulk sediment (former student Patrick Rafter); analysis of the incorporation of various trace and minor elements into diatom frustules (Danny Richter); and the analysis of collection of sclerosponge samples from the outer Seychelles bank that captures the 20th

century record of subsurface Indian Ocean variability (Riley Gannon). Though these activities are difficult to categorize in a simple scientific theme, they are all related in the sense that they involve geochemical tracers of relatively recent ocean/climate change.


Guilderson, T.P. Fallon, S. Moore, M. D., Schrag, D. P. and Charles, C. D. (2009) Seasonally resolved surface water 14C variability in the Lombok Strait: A coralline perspective, J.Geophysical Res. doi:10.1029/2008JC004876

Nurhati, I.S., Cobb, K.M., Charles, C.D. and Dunbar, R.B. (2009) Late 20th century warming and freshening in the central tropical Pacific. Geophysical Res. Letters. Article Number: L21606

Charles C.D., Pahnke, K., Zahn, R., Mortyn, P.G. Ninnemann, U.S., and Hodell, D.A. (2010) Millennial scale evolution of the Southern Ocean chemical divide. Quaternary Science Rev. 29: 399-409

Herguera JC, Herbert T, Kashgarian M, Charles, C.D. (2010) Intermediate and deep water mass distribution in the Pacific during the Last Glacial Maximum inferred from oxygen and carbon stable isotopes. Quaternary Sci. Revs. 29: 1228-1245

Zaunbracher, L, K., Cobb, K.M., Beck, J.W., Charles, C.D., Druffel, E.R.M., Fairbanks, R.G., Griffin, S. and Sayani, H. Coral Records of Central Tropical Pacific radiocarbon variability across the last millennium (in press), Paleoceanography

Catherine ConstableProfessor of GeophysicsEmail: [email protected]

Phone: 858 534 3183

Research interests: Paleomagnetism and geomagnetism, applied to study of long and short term

variations of the geomagnetic field; linking paleomagnetic observations to numerical dynamo

simulations; inverse problems; statistical techniques; electrical conductivity of the mantle; paleo

and rock magnetic databases.

Four existing projects and one new one have received attention over the past year: (i)

geomagnetic field behavior on millennial timescales during the Holocene time period (collaborators

former post doc, Fabio Donadini, now at ETH Zurich, and Monika Korte of GeoForschungs

Zentrum, Helmholtz Center, Potsdam); (ii) the magnetic field on million year time scales (PhD

student Leah Ziegler, and Adjunct Professor Catherine Johnson); (iii) development of modeling and

data processing tools for global electromagnetic induction studies using magnetic field observations

from low-Earth-orbiting satellites (PhD students, Joseph Ribaudo and Lindsay Smith); (iv) the

development with Anthony Koppers and Lisa Tauxe of flexible digital data archives for magnetic

observations of various kinds under the MagIC (Magnetics Information Consortium) database

project. (v) New work has been initiated on a project with postdoctoral researcher Christopher Davies

and research associate David Gubbins with the goal of tuning numerical geodynamo simulations

to provide a realistic reflection of paleomagnetic observations, and a better understanding of core

dynamics.

Figure 1 Variations in strength of the geomagnetic axial dipole for the time interval 0-2 Ma given by

PADM2M in black, and PADM2M.2-40ky filtered version preserving variations at >40kyr periods

in light blue. Red arrows highlight times where there is the tendency for faster growth than decay

as the curve moves towards the present day (0.0 Ma age is the present.)

(i) Holocene Geomagnetic Field Behavior: In 2009 we published a new suite of time-varying

geomagnetic models for the 0-3 ka time interval based on a global compilation of sediment and

archeomagnetic records. Current work is extending these to span the past 10 kyr and conducting syn-

theses of the global secular variation to determine what statistical properties should be reproducible

by numerical dynamo simulations.

(ii) Magnetic Field Variations on Million Year Time Scales: Leah Ziegler recently developed and

applied a maximum likelihood method that uses a combination of absolute geomagnetic paleoin-

tensity data from igneous rocks and archeomagnetic artefacts to simultaneously calibrate individual

time series of relative paleointensity variations derived from marine sediments and recover a contin-

uous representation of paleomagnetic axial dipole moment (PADM) variations for the 0–2 Ma time

interval with about 10 kyr resolution. The result is shown in the estimated variations in the axial

dipole for PADM2M in Figure 1. It is noteworthy that the variations exhibit a form of temporal

asymmetry, with rapid growth often followed by slower decay. This is suggestive of distinctive

physical processes that we hope to be able to understand in our collaborations with Davies and

Gubbins using numerical dynamo simulations.

(iii) Global Electromagnetic Induction: Satellite and observatory magnetic field measurements can

be used for geomagnetic depth sounding to study electromagnetic induction and hence determine

electrical conductivity variations in the deep mantle. Work is targeted to address three major

challenges to acquiring reliable results: (1) accounting for the spatial structure of the external

source field, (2) the impact of near surface heterogeneity on attempts to recover 1-D and 3-D

structure, and (3) effective response estimation across the broadest possible frequency range with

the length of continuous satellite and observatory time series available.

Joseph Ribaudo has been using scripted finite element tools within the commercial software

FlexPDE for flexible 3-dimensional forward modeling to accommodate arbitrary spatial and tempo-

ral variations in external source fields and 3D conductivity variations inside the earth. The method

has now been validated using several analytical models, ranging from 1-dimensional conductivity

shells within the Earth to eccentrically nested spheres. Forward modeling can be conducted in

either the time or frequency domain: the former is particularly useful for satellite observations

where motion of the satellite through a time-varying field can produce spatio-temporal aliasing, and

the method can also accommodate the effects of Earth rotation. Current work is focussed on in-

cluding near surface heterogeneity via a novel application of the magnetic field boundary condition

at Earth’s surface.

Lindsay Smith is exploring the use of multi-taper spectral estimation explicitly designed

to recover frequency-domain response function estimates from data series with inconvenient gaps.

Such gaps which occur as data dropouts in both observatory and satellite data can be especially

limiting at long periods with conventional methods for response estimation. A strategy has been

developed for evaluating the performance of the tapers designed for incomplete sampling, allowing

the user to determine the frequency resolution attainable in the power spectral estimate for any

given distribution of missing observations. Bootstrap methods provide confidence limits on the

spectrum and Monte Carlo simulation is used to assess the reliability of their coverage. The

method has been tested in computing power spectra for several kinds of data, including variations

in length of day, relative geomagnetic paleointensity variations, and a series of external magnetic

field time variations derived from recent satellite missions. Next steps will involve the extension to

cross-spectral techniques for response function estimates.


Hulot, G., C.C. Finlay, C.G. Constable, N.Olsen, & M. Mandea, The magnetic field of planet Earth,

Space Science Reviews, 152, 159-222, doi: 10.1007/s11214-010-9644-0 , 2010.

Donadini, F., M.Korte, & C.G. Constable, Millennial variations of the geomagnetic field: from data

recovery to field reconstruction, Space Science Reviews, , doi:10.1007/s11214-010-9662-y, 2010.

Ziegler, L., C.G. Constable, C.L. Johnson & L. Tauxe, PADM2M: A penalized maximum likelihood

model of the 0-2 Ma paleomagnetic axial dipole moment, Geophys. J. Int., , in review, 2010.

Steven ConstableProfessorEmail: [email protected]

Phone: 4-2409

Research interests: Marine EM methods, conductivity of rocks, satellite in-

duction studies

Steven Constable runs the SIO Marine EM Laboratory along with assistant researcher Kerry Key.

As the name suggests, much of the Lab’s work is involved in developing and using marine EM methods. The

two main techniques are controlled-source EM (CSEM), in which a deep-towed EM transmitter broadcasts

energy to seafloor EM recorders, and magnetotelluric (MT) sounding, in which these same receivers record

natural variations in Earth’s magnetic field. We currently have 4 PhD students, two postdocs, and a research

associate (Arnold Orange) working in the group.

The big data collection expedition for this year was Project SERPENT, 56 MT and CSEM deploy-

ments over the subduction zone offshore Nicaragua. This 28-day NSF-funded cruise aboard the R.V. Melville

was designed to study mantle anisotropy and fluids in the subduction system. See Kerry’s entry in the annual

report for a more complete description of the data collection.

David Myer continued to work on the CSEM and MT data from the Scarborough gas field, and has

re-discovered a zone of extremely high conductivity about 10 km deep in the crust beneath the Exmouth

Plateau, a feature first observed using long-period MT equipment by Graham Heinson of Adelaide University.

This region is thought to be a shear zone associated with extension of the continental shelf, and we hope that

our higher resolution images of part of this structure will help shed light on the origin of this feature. Brent

Wheelock’s work with data collected last year offshore California uncovered some limitations of our existing

instrument calibrations, and so he has spent some time making huge improvements to our calibration data

base (which will benefit most of the projects we are currently working on).

Figure 1. Two approaches to mapping electrical conductivity in the shallow seafloor. The classicalCSEM method (left) uses instruments deployed on the seabed and a transmitter towed 50–100 m abovethe bottom. Our new scheme uses a 3-component electric field receiver (the “Vulcan”, right) towedat a constant offset behind the transmitter. For the deployed receivers, source–receiver geometryprovides depth sensitivity. For the Vulcan, the frequency content of the transmitted signal performsthis function, with low frequencies penetrating deeper into the seafloor.

One area of research, with postdoc Karen Weitemeyer, is the development of marine CSEM methods

for mapping gas hydrate in the seafloor section. Gas hydrate, a frozen mixture of water and gas (mostly

methane), is extremely important for a variety of reasons. It may be an economically viable source of natural

gas, it is a hazard for deepwater drilling, and may be involved in slope failure and rapid climate change, yet

we know little about its distribution in seafloor sediments. Figure 1 shows the approach we are taking to

look for electrically resistive hydrate in shallow (upper 500 m) sediments. One new innovation employs a

3-component receiver towed behind the EM transmitter.

Last year’s annual report described a hydrate data collection cruise to the Gulf of Mexico, and we

are beginning to get results from this. One of the four areas we studied during the October 2008 cruise was

Mississippi Canyon block 118 (MC118), which is in 800–900 m water south-east of New Orleans and has been

designated a hydrate observatory by the Minerals Management Services (now Offshore Energy and Minerals

Management). Hydrate occurs as deposits on the seafloor near a carbonate/hydrate crater complex in the

south-east quadrant of the block, but there has been no previous evidence of hydrate at depth. Geologically,

MC118 is simpler than the other areas we surveyed, and so is a good place to develop our data processing

methods. There is a pipeline and a considerable amount of existing scientific equipment in the observatory,

so being able to tow our transmitter–receiver system 60 m above the seabed gave us a big advantage over the

bottom-dragged resistivity systems other researchers are developing.

MMS Reserve Boundary

Tow 3

Tow 6

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Tow 1

Tow 2

Tow 7

Tow 9

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Fiber O

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Geophysical/Geochemical Sensors

SE complexSW complex

UTM Easting (km)

p

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Figure 2. A: MC118 bathymetry and survey geometry showing tow lines. B: Vulcan data transformedinto apparent resistivities and projected into depth based on the skin depth of the various frequencies wetransmitted. The linear resistivity scale goes from 0.3 to 3 Ωm, with red conductive and blue resistive. Aregion of high resistivity is seen in the south-east quadrant on Tow 5. C: Tow 5 resistivities overlain on chirpacoustic data from Ken Sleeper, http://www.olemiss.edu/depts/mmri/programs/gulf res.html

Figure 2 shows apparent resistivity results from the Vulcan data. The sediment resistivity is remark-

ably uniform at about 1 Ωm except for a region of high resistivity (blue) near the crater complex. Acoustic

chirp data collected by others shows high reflectivity in areas of authigenic carbonate and free gas/hydrate.

Our high resistivities correlate with areas thought to be associated with hydrate and gas, but not areas of

carbonate. This is an important observation – we originally thought that authigenic carbonate would be

resistive and act as a confounding signal when using EM to image hydrate. Unlike massive carbonates, which

tend to be resistive, it appears that in this case the porosity is high enough to prevent a contrast in resistivity.

Further information can be found at the lab’s website, http://marineemlab.ucsd.edu/


Myer, D., S. Constable, and K. Key, A marine EM survey of the Scarborough gas field, Northwest Shelf of

Australia, First Break, 28, 77–82, 2010.

Weitemeyer, K., and S. Constable, Mapping shallow geology and gas hydrate with marine CSEM surveys,

First Break, 28, 97–102, 2010.

J. Peter Davis

Specialist

Email: [email protected]

Phone: 4-2839

Research Interests: seismology, time series analysis, geophysical data acquisition

Peter Davis’s research responsibilities at IGPP center upon managing the scientific performance of Project IDA's portion of the Global Seismographic Network (GSN), a collection of 42 seismographic and geophysical data collection stations distributed among 26 countries worldwide. IDA is in the process of upgrading at all stations the core data acquisition and power system equipment using stimulus funding provided by NSF through the IRIS Consortium. A map of the network showing upgraded systems denoted by orange triangles is shown in Figure 1.

Figure 1. Current data acquisition topology of the IRIS/IDA network.

The GSN has been fully deployed for less than five years, and effort is now being expended to fine tune its performance. Some of Peter Davis’s recent work utilized recording from very large earthquakes as well as the Earth’s tides to evaluate the accuracy of instrument response information published by the GSN. Investigators use this information to compensate for the frequency-dependent sensitivity of sensors so that they may study true ground motion and its underlying physical causes. All GSN network operators including IDA supply this response information along with the seismological time series. Because tides are a continuous background signal observable at nearly all GSN stations not at high latitudes, they are ideal for checking the validity of instrument response over the lifetime of the network. With programs provided by Duncan Agnew of IGPP, Pete computed the tidal signal at all GSN stations to the accuracy required for validating their reported instrument response. This technique was useful both for checking instrument responses and for examining long term changes in the behavior of the network’s sensors.

Although they happen infrequently, very large earthquakes like the Maule, Chile event that occurred in February afford excellent opportunities to verify the accuracy of instrument responses. Figure 2 shows a spectrum of this earthquake at one GSN station in Germany. By measuring the amplitudes of the very gravest modes excited by this quake and comparing the results across all stations of the network, it is possible to identify malfunctioning sensors as well as infer properties of the Earth’s large-scale fine structure.

Figure 2. Spectrum of the 2010 Mw=8.8 Maule, Chile earthquake observed at IRIS/IDA station BFO. The GSN produced spectacular data for this large event, including clear evidence of splitting of 0S2 at single stations such as in this case. Mode 0S0 can be used to assess the quality of the network’s published instrument responses.


Davis, P., and J. Berger, Calibration of the Global Seismographic Network using tides, Seis. Res. Lett., 78, 454-459, 2007.

Davis, P., M. Ishii and G. Masters, An assessment of the accuracy of GSN sensor response information, Seis. Res. Lett., 76, 678-683, 2005.

Park, J., T.-R. Song, J. Tromp, E. Okal, S. Stein, G. Roult, E. Clevede, G. Laske, H. Kanamori, P. Davis, J. Berger, C. Braitenberg, M. Van Camp, X. Lei, H. Sun, H. Xu and S. Rosat, Earth’s free oscillations excited by the 26 December 2004 Sumatra-Andaman earthquake, Science,308, 1140-1144, 2005.

Berger, J., P. Davis, and G. Ekstrom, Ambient Earth Noise: a survey of the Global Seismic Network, J. Geophys. Res., 109, B11307, 2004.

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James Day

Assistant Professor

E-mail address: [email protected] website: http://www.freewebs.com/jmdday/

Research Interests: Solar System formation and evolution; planetary differentiation processes; mantle geochemistry; igneous and metamorphic petrology and volcanology

A broad question in my research is how planets form and evolve. My recent efforts aimed at answering this question include the first measurements of osmium isotopes and precious metals in lunar crustal rocks, providing new insight into the accretion histories of the Earth and Moon (Day et al., 2010a). I recently collaborated on studies of oxygen and iron isotope variations in the Moon (Liu et al., 2010), and mantle heterogeneity in Mars (Basu Sarbadhikari et al., 2009). My recent research on terrestrial igneous systems includes the formation of precious metal deposits in layered mafic intrusions (O’Driscoll et al., 2009), and generation of continental crust (Korhonen et al., 2010). Below, I focus on two specific aspects of my research.

Evolved asteroidal crust: An important new advance in our understanding of planet formation has been the identification of recently discovered paired Antarctic meteorites (GRA 06128/9) as fragments of felsic asteroidal crust (Day et al., 2009a). Most meteorites identified as pieces of asteroid crust are basaltic, but GRA 06128/9 are composed predominantly of sodic plagioclase and are distinctly not basaltic (Figure 1). These meteorites formed by small degrees of partial melting of a volatile-rich asteroid early in Solar System history. We showed that these meteorites derive from an asteroid that did not experience core formation and that they may have formed under similar conditions to an unusual group of meteorites called brachinites, which are predominantly composed of olivine. Combined, GRA 06128/9 and brachinites retain information on some of the earliest stages of planetary differentiation and demonstrate a continuum of lithological compositions generated by melting processes in the early Solar System.

Mantle mysteries: What happens to rocks that are forced down, or subducted, into the mantle at destructive plate margins, such as the Pacific Rim of Fire, and what role do these rocks play in mantle melting? New geochemical data for basaltic lavas from the Canary Islands of El Hierro and La Palma shed new light on what happens to these rocks in the mantle (Day et al., 2009b; 2010b). By using a combination

of oxygen isotopes, which are sensitive indicators of relatively low-temperature hydrothermal alteration at Earth’s surface, and long-lived radioactive isotopes, such as osmium and lead, it has been possible to identify contributions from different portions of recycled oceanic crust and mantle lithosphere in El Hierro and La Palma lavas (Figure 2).

The new results for El Hierro and La Palma are consistent with complex processing of subducted materials in the mantle prior to their ultimate participation in melting to generate ocean islands, such as the Canaries. This result is notable since similar complex processing has been suggested in the mantle beneath the Hawaiian Islands. Other oceanic islands, such as Mangaia (Cook Islands) in the Pacific, are thought to form from recycled materials that are older than those feeding Canary Island volcanoes. Our results provide strong evidence that down-going plate in subduction zones ultimately contributes to modern-day volcanism and that it is possible to detect both variable ages and compositions of this material in ocean island lavas.

Recent Publications Basu Sarbadhikari, A., Day, J.M.D., Liu, Y., Rumble, D. III., Taylor, L.A., 2009. Petrogenesis of olivine-phyric

shergottite LAR 06319: Implications for enriched components in martian basalts. Geochimica et Cosmochimica Acta, 73, 2190-2214.

Day, J.M.D., Ash, R.D., Liu, Y., Bellucci, J.J., Rumble, D. III., McDonough, W.F., Walker, R.J., Taylor, L.A., 2009a. Early formation of evolved asteroidal crust. Nature, 457, 179-182.

Day, J.M.D., Pearson, D.G., Macpherson, C.G., Lowry, D., Carracedo, J.-C., 2009b. Pyroxenite-rich mantle formed by recycled oceanic lithosphere: oxygen-osmium isotope evidence from Canary Island lavas. Geology, 37, 555-558.

Day, J.M.D., Walker, R.J., James, O.B., Puchtel, I.S., 2010a. Osmium isotope and highly siderophile element systematics of the lunar crust. Earth and Planetary Science Letters, 289, 595-605.

Day, J.M.D., Pearson, D.G., Macpherson, C.G., Lowry, D., Carracedo, J.-C., 2010b. Evidence for distinct proportions of oceanic crust and lithosphere in HIMU-type mantle beneath El Hierro and La Palma, Canary Islands. Geochimica et Cosmochimica Acta, doi:10.1016/j.gca.2010.08.021

Korhonen, F.J., Saito, S., Brown, M., Siddoway, C.S., Day, J.M.D., 2010. Multiple generations of granite in the Fosdick Mountains, Marie Byrd Land, West Antarctica: Implications for polyphase intracrustal differentiation in a continental margin setting. Journal of Petrology, 51, 627-670.

Liu, Y., Spicuzza, M.J., Craddock, P.D., Day, J.M.D., Valley, J.W., Dauphas, N., Taylor, L.A., 2010. Oxygen and iron isotope constraints on near-surface fractionation effects and the composition of lunar mare basalt source regions. Geochimica et Cosmochimica Acta, 74, 6249-6262,

O'Driscoll, B., Day, J.M.D., Daly, J.S., Walker, R.J., McDonough, W.F., 2009. Rhenium-osmium isotopes and platinum-group elements in the Rum Layered Suite, Scotland: Implications for Cr-spinel formation and the composition of the Iceland mantle anomaly. Earth and Planetary Science Letters, 286, 41-51.

Catherine de Groot-HedlinAssociate Research Scientist, email: [email protected], Phone extension: 4-2313

Research Interests: Acoustic propagation modeling with application to infrasound and hydroacoustics; application of hydroacoustics and infrasound to nuclear test-ban verification and hazard monitoring; use of dense seismic networks to analyze infrasound signals.Infrasound: A primary goal in infrasound research is to understand the transmission of infrasound - sound at frequencies lower than human hearing - to distances of several hundreds to thousands of kilometers.Shockwaves: de Groot-Hedlin is sole-PI on a project to develop numerical methods to compute the propagation of nonlinear acoustic waves through the atmosphere – this nonlinearity arises when the pressure perturbation associated with acoustic waves is a significant fraction of the ambient atmospheric pressure; such situations can arise from meteoroid explosions in the upper atmosphere or man-made explosions. Infrasound observations at dense seismic networks: de Groot-Hedlin is currently collaborating with other members of the Laboratory for Atmospheric Acoustics (L2A) at UCSD to analyze infrasound signals detected at a dense network of seismic stations operated by the USarray. An analysis of infrasound signals from the re-entry of the space shuttle Atlantis was presented in de Groot-Hedlin et al. (2008a). Currently, the L2A group is working on the analysis of infrasound signals at this network generated by explosions at the Utah Test and Training Range (UTTR), see Figure 1.

Figure 1. (left) A map of the configuration of the USarray seismic network in June 2007 (circles), also showing the source location (diamond) and sites of infrasound arrays (triangles). Signals at sites within 600 km of the source (dark circles) were analyzed. (right top) Observed celerities (=horizontal range/time). (right bottom) Predicted celerities.

The presence of the transportable USArray in this region provided this study with a much broader and denser array of sensors than would otherwise be available. Arrival times, predicted using standard atmospheric specifications that give variations in wind and sound speed with altitude, indicate that the arrivals are mulit-pathed; the earlier arrivals are ducted within the thermosphere, later ones are refracted within the stratosphere. An unexplained observation is the presence of high frequency infrasound arrivals, near the acoustic frequency band. This suggests that propagation may be non-linear at upper altitudes, where non-linear steepening of the sound waves can take place to maintain the higher acoustic frequencies. Propagation algorithms to explain this phenomenon are under development.

Hydroacoustics: Work is continuing on the analysis of hydroacoustic data recorded on hydrophones that comprise part of the global International Monitoring System (IMS) network. In the past, data from IMS hydrophones has been used to investigate the generation of ocean-borne sound waves by submarine earthquakes (de Groot-Hedlin and Orcutt, 1999 and 2001), the rupture of the 2004 Great Sumatran rupture, that released a devastating tsunami (de Groot-Hedlin, 2005), as well as a series of investigation into long-range acoustic propagation in the Indian Ocean (Blackman et.al., 2004) and through the Antarctic Circumpolar Current (de Groot-Hedlin et.al., 2009).

Relevant Publications de Groot-Hedlin, C.D., and J.A. Orcutt, 1999, Synthesis of earthquake-generated T-

waves, Geop. Res. Lett., 26, 1227-1230. de Groot-Hedlin, C.D., and J.A. Orcutt, 2001, T-phase observations in northern

California: Acoustic to seismic coupling at a weakly elastic boundary, PAGEOPH,158, 513-530.

Blackman, D.K., C. de Groot-Hedlin, P. Harben, A. Sauter, and J.A. Orcutt, 2004, Testing low/verylow frequency acoustic sources for basin-wide propagation in the Indian Ocean, J.Acoust. Soc. Am., 116, 2057-2066.

de Groot-Hedlin, C.D., M.A.H. Hedlin, K.T. Walker, D. D. Drob, and M.A. Zumberge, Evaluation of infrasound signals from the shuttle Atlantis using a large seismic network, J. Acoust. Soc. Am., 124, 1442-1451, (2008a)

de Groot-Hedlin, C.D., Finite-difference synthesis of infrasound propagation through an absorbing atmosphere, J. Acoust. Soc. Am., 124, 1430-1441, (2008b)

de Groot-Hedlin, C.D., D.K. Blackman, and C.S. Jenkins, 2009, “Effects of variability associated with the Antarctic Circumpolar Current on sound propagation in the ocean”, Geop. J. Int., 176, 478-490 (2009)

Herrin, E.T., Bass, H.E., B. Andre, R.L. Woodward, D. D. Drob, M.A.H. Hedlin, M.A. Garces, P.W. Golden, D.E. Norris, C.D. de Groot-Hedlin, K.T. Walker, C.A. L. Szurbela, R.W. Whitaker, and F.D. Shields, High-altitude infrasound calibration experiments, Acoustics Today, 4, 9-21, (2008)

Matoza, R.S., M.A. Garces, B.A. Chouet, L., D’Auria, M.A.H. Hedlin, C. de Groot-Hedlin, and G.P. Waite, 2009, “The source of infrasound associated with long-period events at Mount St. Helens”, accepted by Journal of Geophysical Research (Solid Earth), 114, B04305, doi:10.1029/2008JB006128.

Neal Driscoll

Professor of Geology


Phone: 858-822-5026

Research Interests: Landscape and seascape evolution in response to tectonic deformation, sea-level fluctuations, and climate; neotectonics and geohazards

The 2004 Boxing Day Sumatran 9.0 magnitude earthquake and consequent tsunami brought into sharp focus the need to understand potential geohazards. My research group is assessing potential geohazards both onshore and offshore. We have developed state-of-the-art instrumentation and technologies to investigate the structure and evolution of continental margins as well as the physical processes controlling geohazards (i.e., earthquakes and slope failure). The overarching goal of my research group is to understand geohazards and how they initiate and evolve so we can apply that knowledge to develop hazard risk assessment as well as

develop models, policies, and strategies for hazard mitigation.

Rupture direction on large faults (e.g., San Andreas) plays a large role in the predicted magnitude of ground shaking – what controls this process? What is the earthquake recurrence interval for major fault systems in California? Is the time since the last great quake greater than or less than the earthquake recurrence interval for a given fault segment? How do faults move? How is strain communicated and partitioned between neighboring fault systems in the Californias? Answers to these questions will improve seismic hazard identification and help develop improved quantitative models, both of which are necessary first steps toward developing strategies for geohazard mitigation.

In addition, my research group is interested in determining how coastal regions will be impacted by larger storms and rising sea level predicted by global warming models. The nearshore region is facing increased pressures from fisheries, land development, and contaminated runoff, just to name a few. Our understanding of depositional and erosional processes in nearshore regions (e.g., beaches, sea cliffs, inner shelf) remains

limited and thus it is difficult to predict the response of the nearshore to increased storminess and sea level rise. Sea level is rising at an unprecedented rate of 2 - 3 mm/yr due to global warming and raises concerns about the stability of beaches and adjacent sea cliffs. We are using ground-based 3D laser

scanning (LIDAR) to quantify the erosion rate of the sea cliffs through time. The LIDAR data together with sediment grain size analysis of the failures allows us to define the volume of sand liberated by cliff erosion that remains on the beach. We have been examining the fate of ten failures in a 6.5 km stretch of coastline in the Oceanside Littoral Cell to assess their volumetric impact on the coastal sediment budget.

Selected Publications: Brothers, D.S., Driscoll, N.W., Kent, G.M., Harding, A.J., Babcock, J.M., and Baskin, R.L. (2009).

Tectonic evolution of the Salton Sea inferred from seismic reflection data. Nature Geoscience 2, 581-584; doi:10.1038/ngeo590.

Dingler, J., Kent, G., Driscoll, N., Babcock, J., Harding, A., Seitz, G., Karlin, B., and Goldman, C. (2009). A high-resolution seismic CHIRP investigation of active normal faulting across the Lake Tahoe Basin, California-Nevada. Geological society of America Bulletin, v. 121. DOI: 10.1130/B26244.1.

Hill J.C. and N. W. Driscoll (2010). Iceberg discharge to the Chukchi Shelf during the Younger Dryas. Quaternary Research, v. 74: 57-62.

Le Dantec, N., Hogarth, L., Driscoll, N., Babcock, J., Barnhardt, W., and Schwab, W. (2010). Tectonic Controls on Nearshore Sediment Accumulation and Submarine Canyon Morphology Offshore La Jolla, Southern California. Marine Geology, V.268:115-128

Olsen, M.J, Johnstone, E., Driscoll, N., Ashford, S., and Kuester, F. (2009). Terrestrial Laser Scanning of Extended Cliff Sections in Dynamic Environments: Parameter Analysis. ASCE Journal Of Surveying Engineering 135(4): 161-169.

Young, A., Olsen, M., Driscoll, N., Flick, R., Gutierrez, R., Guza, R., Johnstone, E., and Kuester, F. (2010). Comparison of Airborne and Terrestrial LIDAR Estimates of Seacliff Erosion in Southern California. Photogrammetric Engineering & Remote Sensing, V.76: 421-427.

Matthew DzieciuchProject ScientistEmail: [email protected]: 4-7986

Research interests: acoustical oceanography, ocean acoustic tomography, signal process-ing

Philippine Sea Experiment

Over the past year I have been partipating in an ocean acoustic tomography ex-periment. The experiment has been funded by the Office of Naval Research and is takingplace in the Philippine Sea starting in 2009 and ending in 2011. This location is in a chal-lenging and dynamic part of the ocean, which is located near, but not in the origin of amajor western boundary current, the Kuroshio. The program has two main goals, one isoceanographic in nature, and the second explores acoustic issues.

It has been speculated from recent modeling work (see the third paper referencedbelow) that ocean basin western boundary currents radiate barotropic waves that carrya large amount of energy with them. These are difficult to detect with standard oceano-graphic instrumentation but should be possible to detect with a tomographic array likethe one that we have designed. A secondary purpose is to find the limits of ocean modelpredictability given the strong constraints of the tomography data and thus improve modelperformance. This questions will be explored with data to be taken during the upcomingyear-long deployment of a tomographic array.

The second goal is to continue to explore the limits of ocean acoustic systems whosetime and space coherence scales are limited by the ocean’s dynamics. Since this experimentallocation is in a much more energetic location than previous ones in the North Pacific, itwill be interesting to see how stable the acoustic paths are in this area. Differences instratification, and increased mesoscale energy, are expected to strongly influence the results.

Some preliminary results are already available from a month-long engineering de-ployment of a vertical line array of receivers this past April. This array featured 60internally-recording autonomous hydrophones that are capable of recording 16 Gbytes ofacoustic data. The first-time deployment of this array was configured with 30 hydrophonesspaced 25m apart near the sound-channel axis at 1000m, and 30 more hydrophone spanningthe surface conjugate depth at about 4600m.

The figure below shows the minimum noise power recorded on the vertical line arrayas a function of depth. The scientific interest here is to explain the reduction of power withdepth and frequency. The minimum noise level is thought to be a combination of distantshipping traffic and wind-driven ocean turbulence near the surface. The figure confirmsresults that others have qualitatively described, but the data are meant to give a very goodquantitative measurement of the effect. The challenge will be to develop a model that hasactual predictive power based on wind-speed and shipping traffic density.

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Dushaw, B. D., Worcester, P. F., Munk, W. H., Spindel, R. C., Mercer, J. A., Howe, B.M., Metzger, K., Jr., Birdsall, T. G., Andrew, R. K., Dzieciuch, M. A., Cornuelle,B. D., and Menemenlis, D., A decade of acoustic thermometry in the North PacificOcean, J. Geophys. Res., 114, C07021, (2009).

Van Uffelen, L. J., Worcester, P. F., Dzieciuch, M. A., and Rudnick, D. L., The verticalstructure of shadow-zone arrivals at long range in the ocean, J. Acoust. Soc. Am.,125, 35693588. (2009).

Miller, A.J., Neilsen, D.J., Luther, D.S., Hendershott, M.C., Cornuelle, B.D., Worces-ter, P.F., Dzieciuch, M.A., Dushaw, B.D., Howe, B.M., Levin, J.C., Arango, H.G.,and Haidvogel, D.B., Barotropic Rossby wave radiation from a model Gulf Stream,Geophysical Research Letters, 34 (23), [DOI 10.1029/2007GL031937], (2007).

Dzieciuch, M., W. Munk, and D. Rudnick, Propagation of sound through a spicy ocean,the SOFAR overture, J. Acoust. Soc. Am., 116, 1447-1462, (2004).

Dzieciuch, M., P. Worcester, and W. Munk, Turning point filters: Analysis of soundpropagation on a gyre-scale, J. Acoust. Soc. Am., 110, 135-149, (2001).

Yuri FialkoProfessorEmail: [email protected]: 2-5028

Research interests: earthquake physics, crustal deformation, space geodesy, volcanology

Yuri Fialko’s research is focused on understanding the mechanics of seismogenicfaults and magma migration in the Earth’s crust, through application of principles of con-tinuum and fracture mechanics to earthquakes and volcanic phenomena. Prof. Fialko isusing observations from space-borne radar satellites, including the ERS and ENVISATsatellites of the European Space Agency, and the ALOS satellite of the Japanese SpaceAgency, as well as the Global Positioning System, to investigate the response of the Earth’scrust to seismic and magmatic loading.

An ongoing transition of space geodesy from a data-poor to a data-rich disciplinewarrants increasingly sophisticated models of deformation of the Earth that take into ac-count material heterogeneities (generally, in three dimensions), and time-dependent behav-ior such as fault creep, viscoelastic relaxation, and poroelastic effects. A former graduatestudent Sylvain Barbot (now a postdoctoral fellow at Caltech) has been developing a frame-work for a generalized viscoelastoplastic rheology whereby some inelastic strain relaxes aphysical quantity in the material. The relaxed quantity is the deviatoric stress in caseof viscoelastic relaxation, the shear stress in case of creep on a fault plane and the traceof the stress tensor in case of poroelastic rebound. In this framework, the instantaneousvelocity field satisfies the linear inhomogeneous Navier’s equation with sources parameter-ized as equivalent body forces and surface tractions. The surface velocity field is evaluatedusing the Fourier-domain Green’s function for an elastic half-space with surface buoyancyboundary condition. The proposed method allows one to model post-seismic transients thatinvolve multiple mechanisms (afterslip, poroelastic rebound, ductile flow) with an accountfor the effects of gravity, non-linear rheologies and arbitrary spatial variations in inelasticproperties of rocks (e.g. the effective viscosity, rate-and-state frictional parameters andporoelastic properties).

In collaboration with a former postdoc Jill Pearse (now a research scientist at theNASA’s Jet Propulsion Laboratory), Prof. Fialko investigated long-term deformation dueto the Socorro Magma Body (SMB) in central New Mexico. The SMB is one of the largestactive intrusions in the Earth’s continental crust. This project involved elaborate measure-ments using Interferometric Synthetic Aperture Radar (InSAR) observations and equallyelaborate finite element simulations. InSAR data spanning 15 years (1992-2007) indicatethat the magma body is associated with a steady crustal uplift at a rate of about 2 mm/yr.Figure 1 shows a remarkable agreement of old leveling data with new InSAR measurements,suggesting that the uplift persisted at a constant rate over the last century. Our previouswork (e.g., Fialko et al., 2001) showed that while the pattern of surface uplift is consistentwith an elastic inflation of a large sill-like magma body, the SMB could not have formed viasteady elastic inflation because the latter would be outpaced by magma solidification. Weresolve this problem using coupled thermovisco-elastic models, and place constraints on theintrusion history as well as the rheology of the ambient crustal rocks. We demonstrate thatobservations rule out the linear Maxwell response of the ductile crust, but are consistentwith laboratory-derived power law rheologies. Our preferred model suggests that the ageof the SMB is of the order of 103 years, and that the apparent constancy of the present-dayuplift may be due to slow heat transfer and ductile deformation in a metamorphic aureoleof a giant sill-like magma intrusion, rather than due to a steady increase in the magma over-

Figure 1: Acomparison ofuplift rate inferredfrom leveling dataspanning a timeperiod from 1912to 1951 (solidgreen line) andsatellite lin-of-sight velocityinferred fromInSAR data span-ning a time periodfrom 2000 to 2006(blue circles).

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pressure. The SMB is a contemporaneous example of “magmatic intraplating,” a processby which large volumes of mafic melt stall and spread at midcrustal depths due to densityor rheology contrasts.

Another area of Prof. Fialko’s research interests involves modeling of deformationdue to large crustal earthquakes. The object of a most recent study was the Mw 7.9Wenchuan (China) earthquake of 2008. Available interferometric synthetic aperture radar(InSAR) data provided a nearly complete coverage of the surface deformation along bothascending (fine beam mode) and descending orbits (ScanSAR to ScanSAR mode). The bestfit model has fault planes that rotate from shallow dip in the south (35 degrees) to nearlyvertical dip toward the north (70 degrees). The inferred rupture model is complex withvariations in both depth and rake along two major fault strands. Our model suggests thatmost of the moment release was limited to the shallow part of the crust (depth less than10 km). Interestingly, aftershocks were primarily distributed below the section of the faultthat ruptured coseismically.


Barbot, S. and Y. Fialko (2010), A unified continuum representation of postseismic re-laxation mechanisms: Semi-analytic models of afterslip, poroelastic rebound and vis-coelastic flow, Geophys.J.Int., 182, 1124-1140.

Pearse, J. and Y. Fialko (2010), Mechanics of active magmatic intraplating in the RioGrande Rift near Socorro, New Mexico, J.Geophys.Res., 115, B07413.

Barbot, S. and Y. Fialko (2010), Fourier-domain Green function for an elastic semi-infinite solid under gravity, with applications to earthquake and volcano deformation,Geophys.J.Int., 182, 568-582.

Tong, X., D. Sandwell, and Y. Fialko (2010), Coseismic slip model of the 2008 Wenchuanearthquake derived from joint inversion of interferometric synthetic aperture radar,GPS, and field data, J.Geophys.Res., 115, B04314.

Helen Amanda Fricker

Associate Professor



Research Interests: cryosphere, Antarctic ice sheet, subglacial lakes, ice shelves, satellite laser altimetry

Helen Amanda Fricker’s main research focuses on the Earth's cryosphere, in particular the Antarctic ice sheet. She leads the Scripps Glaciology Group which currently has two postdocs (Sasha Carter and Fabian Walter) and three graduate students (Linghan Li, Fernando Paolo and Matthew Siegfried). One of the primary questions in Antarctica is whether its mass is changing due to climate change. Due to its vast size, and the long time periods over which it can change, satellite data are crucial for routine monitoring of Antarctica, in particular data from radar and laser altimetry, and also imagery. Since the launch of NASA’s Ice, Cloud & land Elevation Satellite (ICESat) in January 2003 Helen has used ICESat laser altimetry, which provides accurate elevation data for ice sheet change detection. She has been affiliated with the ICESat Science Team since 1999 and has been a Team Member since April 2006. She is also a member of the ICESat-II Science Definition Team (since December 2008). In 2010 Helen was awarded the Martha T. Muse prize for her contribution to Antarctic research.

Antarctic subglacial water: In 2006 Helen and her colleagues discovered active subglacial water systems under the fast-flowing ice streams of Antarctica using ICESat data. They found large elevation change signals in repeat-track ICESat data (up to 10m in some places) corresponding to draining and filling of subglacial lakes beneath 1-2 km of ice. Changing the basal conditions of an ice sheet, particularly beneath fast flowing ice streams and outlet glaciers, is one possible mechanism to increase its contribution to sea level rise, through increased ice flow rates in the ice streams. With the current interest in Antarctic ice sheet mass balance and its potential impact on sea-level rise, it is important to understand the subglacial water process so that it can become incorporated into models; IGPP postdoc Sasha Carter works with Helen on this aspect of the problem. Her team continues to monitor active lakes, and have found 124 in total throughout Antarctica. Helen is now a PI on a large, interdisciplinary project (Whillans Ice Stream Subglacial Access Research Drilling; WISSARD) to drill into one of the subglacial lakes that she discovered – Subglacial Lake Whillans (SLW) on Whillans Ice Stream (WIS; Figure 1) – and the region of the grounding line across which the subglacial water flows.

Figure 1. a) Map of WIS lake system with annotation of the estimated flowpath from SLW to the grounding line. Inset maps show the location of WIS in Antarctica (McM is McMurdo Station); b) averaged time series of estimated surface elevation and volume changes since Oct 2003 for SLW.

Ice shelf grounding zones: Helen and her group also use ICESat data to map the grounding zones (GZs) of the ice shelves - the dynamically-active transition zones between grounded and floating ice. GZs are important because they are the gateway through which ice flows off the grounded ice sheet into the ice shelves and ultimately to the ocean; monitoring them is an important part of ice sheet change detection. Her analysis of data from repeated tracks, sampled at different phases of the ocean tide, has shown that ICESat can detect the tide-forced flexure zone in the GZ, providing accurate GZ location and width information for each track. In 2009-2010 Helen and IGPP postdoctoral researcher Kelly Brunt (now at GSFC) used this technique to map the GZ for all of Antarctica, see Brunt and others (2010). This combined with surface elevation at the grounding lines will contribute to improved calculations of the ice sheet’s mass balance.

Glacio-seismology: In 2009-2010 Helen also worked on an NSF project with Jeremy Bassis and Shad O’Neel (both ex-IGPP postdocs) investigating the source processes for seismic signals recorded in three different glaciological environments: the Amery Ice Shelf; the Ross Ice Shelf; and Columbia Glacier, Alaska. IGPP postdoc Fabian Walter works on this project, and published a paper on the changing calving style of the Columbia Glacier before and after its terminus became floating, assessed through changes in seismic signals.

Publications June 2009-Sept 2010

FRICKER, H.A., R. POWELL, J. PRISCU, S. TULACZYK, S. ANANDAKRISHNAN, B. CHRISTNER, D. HOLLAND, H. HORGAN, R. JACOBEL, J. MIKUCKI, A. MITCHELL, R. SCHERER, J. SEVERINGHAUS (2010). Siple Coast Subglacial Aquatic Environments: The Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project. In Subglacial Antarctic Aquatic Environments (M. Siegert, C. Kennicutt, B. Bindschadler, eds.). AGU Monograph. Washington DC.

WALTER, F., S. O'NEEL , D. E. MCNAMARA , W. T. PFEFFER , J. BASSIS, H. A. FRICKER (2010) Iceberg calving during transition from grounded to floating ice: Columbia Glacier, Alaska, Geophys.Res. Letts., 37, L15501, 5 PP., 2010 doi:10.1029/2010GL043201. For press release see: http://scrippsnews.ucsd.edu/Releases/?releaseID=1080.

BRUNT, K.M., M.A. KING, H. A. FRICKER and D.R. MACAYEAL (2010) Flow of the Ross Ice Shelf, Antarctica, is modulated by the ocean tide, Journal of Glaciology, 56(195), 157-161.

BRUNT, K.M., H. A. FRICKER, L. PADMAN, T.A. SCAMBOS, S. O’NEEL (2010) Mapping the grounding zone of the Ross Ice Shelf, Antarctica, using ICESat laser altimetry, Annals of Glaciology, 51(55), 71-79.

FRICKER, H.A., T. A. SCAMBOS, S. CARTER, C. DAVIS, T. HARAN, I. JOUGHIN (2010) Synthesizing multiple remote-sensing techniques for subglacial hydrologic mapping: application to a lake system beneath MacAyeal Ice Stream, West Antarctica, Journal of Glaciology, 56(196), 187-199.

W. ABDALATI, H. J. ZWALLY, R. BINDSCHADLER, B. CSATHO, S. L. FARRELL, H. A. FRICKER,D. HARDING, R. KWOK, M. LEFSKY, T. MARKUS, A. MARSHAK, T. NEUMANN, S. PALM, B. SCHUTZ, B. SMITH, J. SPINHIRNE, C. WEBB (2010), The ICESat-2 Laser Altimetry Mission, Proceedings of the IEEE, 98(5), 735-751.

SMITH, B., H.A. FRICKER, I. JOUGHIN, S. TULACZYK (2009) An Inventory of Active Subglacial Lakes in Antarctica Detected by ICESat (2003-2008), Journal of Glaciology, 55(102), 573-595.

CRAVEN, M., I. ALLISON, H.A. FRICKER, R.C. WARNER (2009) Properties of a marine ice layer under the Amery Ice Shelf, Journal of Glaciology, 55(192), 717-728.

FRICKER, H.A., R. COLEMAN, L. PADMAN, T.A. SCAMBOS, J. BOHLANDER, K.M. BRUNT (2009) Mapping the grounding zone of the Amery Ice Shelf, East Antarctica using InSAR, MODIS and ICESat, Antarctic Science, 21(5), 515-532.

Jeff Gee

Professor



Research Interests: application of paleomagnetic and magnetic anomaly data to crustal accretionary processes at mid-ocean ridges and past geomagnetic field variations; origin and significance of magnetic fabrics in igneous rocks.

Although the directional variations of the geomagnetic field are relatively well known, fluctuations in the intensity of the field and even it's average intensity are more uncertain. In part this is because accurate estimates of the ancient field intensity require fine grained magnetic minerals that are also stable to the multiple laboratory heatings that are typically used in paleointensity experiments. Few geological materials fulfill both these criteria and so new materials that might be suitable for estimating the past geomagnetic intensity are highly sought.

Timing of magnetite formation in submarine basaltic glass: Submarine basaltic glass (SBG) has been increasingly used in recent years to recover geomagnetic paleointensity variations. A high percentage of specimens demonstrate ideal behavior in step-wise reheating experiments designed to recover paleointensity estimates, primarily because of the small grain size of the magnetite particles (compared to basalt) and the fact that the glassy matrix may protect the particles against thermochemical alteration during the experiments. Because the origin of the fine grained low-Ti magnetite in SBG is uncertain, the validity of paleointensity data from glasses has been questioned. We synthesized basaltic glasses under controlled conditions, varying the oxygen fugacity, cooling rate and glass composition to determine whether magnetite is an original phase in such quenched glasses (Fig. 1) and whether they accurately record the ambient magnetic field. Results of this study (Bowles et al., in review) indicate that low-Ti magnetite is an original phase, formed during rapid quenching of the glass which has magnetic properties similar to natural glasses and accurately record the ambient field. A companion study (Burgess et al., 2010) indicates that the magnetic phase is not dramatically altered by heating at temperatures below the glass transition temperature (~680°C); together these results indicate that SBG should have a primary thernoremanence and be an accurate recorder of geomagnetic field intensity.

Figure 1: Transmitted light images of synthetic glass samples used for paleointensity study. A zone of plagioclase adjacent to the crucible wall transitions to a spherulitic zone and then glass in slowly-cooled sample (left). In quickly-cooled sample (right) a continuous spherulitic zone is absent although small spherulitic regions are found at the tips of plagioclase crystals. Paleointensity experiments on both glassy and spherulitic glasses accurately reproduce the ambient field.

Ignimbrites as a possible new material for paleointensity studies: Ash flow tuffs (ignimbrites) are known to contain fine-grained magnetite that should be suitable for estimating geomagnetic field intensity. However, the magnetization of ignimbrites may include both thermal and chemical remanence as a result of the complex magnetic mineralogy and variations in the thermal and alteration history. Initial results from the 0.76Ma Bishop Tuff provided internally consistent intensity estimates (Gee et al., 2010). In the summer of 2010 we sampled two historical ignimbrites – the 1980 ash flows at Mt. St. Helens, Washington, and the 1912 flows from Novarupta in the Valley of Ten Thousand Smokes, Alaska – that provide a natural laboratory for testing measured paleointensities against known field values. Direct temperature measurements at both localities constrain the emplacement temperature, and significant information is available on the conditions of post-emplacement fumarolic activity. Combined with focused studies in the older, better-exposed Bishop Tuff, our sampling strategy will allow us to evaluate the suitability of ignimbrites for paleointensity analysis, as well as the feasibility of identifying (in the field or lab) samples most likely to provide reliable results.

Figure 2: 1912 ignimbrite in the Valley of Ten Thousand Smokes, Alaska. (left) Aerial view of narrow gorge, up to 30m deep, along Lethe river in the upper valley. (right) Preparing to sample in the gorge.

Recent Publications

Gee, J.S., Y. Yu, and J. Bowles, 2010, Paleointensity estimates from ignimbrites: an evaluation of the Bishop Tuff, Geochem. Geophys. Geosystems, 11(3), Q03010, doi: 10.1029/2009GC002834.

Burgess, K., Cooper, R.F., Bowles, J.A., Gee, J.S. and D.J. Cherniak, 2010, Effects of open and closed system oxidation on texture and magnetic response of remelted basaltic glass, Geochem. Geophys. Geosystems, 11(10), Q10007, doi: 10.1029/2010GC003248.

Bowles, J.A., Gee, J.S., Burgess, K. and R.F. Cooper, 2010, Timing of magnetite formation in submarine basaltic glass: a comparison of natural and synthetic samples with implications for geomagnetic paleointensity analyses, Geochem. Geophys. Geosystems, in review.

Granot, R., S.C. Cande, and J.S. Gee, 2009, The implications of long-lived asymmetry of remanent magnetization across the North Pacific fracture zones, Earth Planet. Sci. Lett., 288, 551-563.

Morris, A., Gee, J.S., Pressling, N., John, B.E., MacLeod, C.J., Grimes, C.B. and R.C. Searle, 2009, Footwall rotation in an oceanic core complex quantified using reoriented Integrated Ocean Drilling Program core samples, Earth Planet. Sci. Lett., 287: 217-228.

Alistair HardingResearch GeophysicistEmail: [email protected]: 44301Research Interests: Marine seismology, mid-ocean ridges, continental rifting, tectonic hazards in California

The southern terminus of the modern San Andreas fault lies along the eastern shore of the Salton Sea in the Imperial Valley east of San Diego. Just to the north the San Andreas undergoing transpression within the Durmid Hills but to the south the nature of the deformation is poorly understood. The Brawley seismic zone outlines a band of deformation passing beneath the southern Salton Sea that connects San Andreas to the Mesquite basin at the northern end of the Imperial fault. The right-lateral jog between the Imperial and San Andreas faults should produce transtension within the step over region but in the absence of active seismic imaging models of deformation have had to rely primarily on the historic seismicity patterns.

In April and May 2010, we conducted a pilot MCS survey of the Salton Sea collecting approximately 460 km of data in a 13 day survey. The investigators included Dr. Alistair Harding & Prof. Neal Driscoll from Scripps, Prof. Graham Kent from University of Nevada, Reno, Rob Baskin from the USGS, and Mike Barth from Subsea Systems who provided the equipment. We used a three-tipped sparker system as a source and a digital 24 channel streamer with 3.125 m group spacing with a maximum offset of 84 m as a receiver. In general data quality was excellent in areas without near-surface gas accumulations with detailed stratigraphy recorded down to ~500-800 m. This survey was a follow up to our earlier high-resolution Chirp survey of the sea (Brothers et al, 2009; doi:10.1038/NGEO590).

Preliminary processing of the MCS lines reveals a divergent wedge of sedimentary material in the upper part of the section that systemically thickens towards the southern shore of the Salton Sea, Figure 1. The divergence records the onset of the rapid subsidence in the southern part of the Sea, south of the San Andreas. If modern sedimentation rates of 1-2 cm/yr are representative of earlier rates then rapid subsidence, >5 mm/yr, has been ongoing for the last 10-20 kyr. This result is consistent with the earlier Chirp survey results which revealed subsidence > 6mm/yr for the last few thousand years. It is possible that the onset of subsidence was triggered by the northern propagation of the Imperial fault, creating the active step over with the San Andreas

Figure 1: Preliminary processing of line 10 (red line on map left) taken from the 400+ km of lines collected during the survey ( greens lines on map). There is pronounced divergence above the yellow horizon as well as a marked change in the acoustic character. Beneath the yellow horizon the layering is predominantly parallel and mostly concordant. The hinge for the divergent wedge is roughly perpendicular to the southern end of the San Andreas.

San Andreas

Michael A.H. Hedlin




Research Interests: Analysis of acoustic signals from large-scale atmospheric phenomena; study of seismo-acoustic phenomena, nuclear test-ban verification.

Infrasound: The study of subaudible sound, or infrasound, has emerged as a new frontier in geophysics and acoustics. We have known of infrasound since 1883 with the eruption of Krakatoa, as signals from that event registered on barometers around the globe. Initially a scientific curiosity, the field briefly rose to prominence during the 1950’s and 1960’s during the age of atmospheric nuclear testing. With the recent Comprehensive Test-Ban Treaty, which bans nuclear tests of all yields in all environments, we have seen renewed interest in infrasound. A worldwide network of infrasound arrays, being constructed ostensibly for nuclear monitoring, is fueling basic research into man-made and natural sources of infrasound, how sound propagates through our dynamic atmosphere and how best to detect infrasonic signals amid noise due to atmospheric circulation.

Research at L2A: The new Laboratory for Atmospheric Acoustics (L2A) is the home of research in this field at IGPP. Several faculty, post-docs and PhD students work full or part time in L2A, supported by engineers and technicians in the lab and the field. Presently we study a broad suite of problems related to both natural and man-made sources.

Seismic network observations of atmospheric events: The global infrasound network is unprecedented in scale however it is still very sparse, with on the order of 100 stations operating worldwide. To increase the density of sampling of the infrasonic wavefield to study atmospheric phenomena and propagation of infrasound through the atmosphere we have used acoustic–to-seismic coupled signals recorded by dense regional seismic networks, such as the 400-station USArray. We have studied propagation from large bolides and other events, such as large explosions. The seismic network is allowing us to study in detail acoustic branches from large atmospheric events that are akin to seismic branches. We are using the network to create a catalog of atmospheric events in the United States similar to commonly used seismic event catalogs. The acoustic catalog is used in part to find sources of interest for further study and to identify regions where large atmospheric events are prevalent.

USArray upgrade: We were recently funded to upgrade the USArray with infrasound microphones and barometers. Our sensor package will be sensitive to air pressure variations from D.C. to 20 Hz, at the lower end of the audible range. We expect that over the coming year the entire USArray will be retrofitted with these new sensors to create the first-ever semi-continental-scale seismo-acoustic network. The network will span ~ 2,000,000 square km in the eastern United States before being redeployed in Alaska.

Miscellaneous studies: 1) Ocean noise: Using data from our permanent array in the Anza-Borrego desert and two more arrays near San Diego we detect surf noise from along the coast of California. Infrasonic waves from the crashing surf propagate through the stratosphere to our stations up to 200 km away. We see further avenues for research in this area in that lower frequency signals, known as microbaroms, are known to propagate 1000’s of km and can be used to probe atmospheric structure. 2) Natural hazards: Our group is using infrasound energy to detect and monitor emerging hazards (such as volcanic eruptions, major storms at sea, tornadoes).

We are particularly interested in the use of infrasound sensors to monitor volcanoes, such as Mount Saint Helens, that have a history of releasing ash into the stratosphere. 3) Study of seismo-acoustic phenomena: The Earth’s free-surface is rich in sources that generate both downgoing seismic and upgoing acoustic energy. We believe to properly characterize such sources it is necessary to study the entire seismo-acoustic wavefield. We have recently completed a study of Mount Saint Helens using both types of sensors (Robin Matoza, PhD thesis). Studies of other seismo-acoustic sources (such as shallow earthquakes) are currently underway.

Field operations: Our group has built two permanent infrasound arrays in the US and one in Africa. In recent years we have deployed infrasound arrays across the southwestern US to record signals from high-altitude explosions and natural phenomena. We currently operate research arrays located near San Diego with another to be deployed near Chico, California in late 2010. A typical temporary array comprises 4 to 8 aneroid microbarometers or fiber-optic sensors spanning an area 100 to 300 meters across, with data recorded using 24-bit Reftek digitizers and telemetered in realtime to our lab in La Jolla. We use Sun workstations and a suite of Macintosh G5 computers. All data from the field is archived on a multi-TB RAID. All computers, and supporting peripherals such as printers, are linked via a broadband communications network.

Relevant Publications Arnoult, K., Olson, J., Szuberla, C., McNutt, S., Garces, M., Fee, D. and Hedlin, M.A.H., 2010, Infrasound observations of the 2008 explosive eruptions of Okmok and Kasatochi volcanoes, Alaska, Journal of Geophysical Research – Atmospheres (in press). Arrowsmith, S.J., Drob, D.P., Hedlin, M.A.H. and Edwards, W., 2006, A joint seismic and acoustic study of the Washington State bolide: Observations and modeling, in review with Journal of Geophysical Research. v112, D09304, doi:10.1029/ 2006JD008001.Arrowsmith, S. & Hedlin, M.A.H., 2005, Observations of infrasound from surf in Southern California, Geophysical Research Letters, 32, No. 9, L09810,doi:10.1029/2005GL022761. Arrowsmith, S.J., Johnson, J.B., Drob, D. and Hedlin, M.A.H., 2010, The seismo-acoustic wavefield: A new paradigm in studying geophysical phenomena, Reviews of Geophysics (in press). Bass, H., Bhattacharyya, J., Garces, M., Hedlin, M.A.H., Olson, J. and Woodward, R., 2006, Infrasound, Acoustics Today, 2, 9-19. de Groot-Hedlin, C.D., Hedlin, M.A.H., Walker, K., Drob., D., and Zumberge, M., 2008, Study of propagation from the shuttle Atlantis using a large seismic network, J. Acoust. Soc. Am., 124, 1442-1451.de Groot-Hedlin, C.D., Hedlin, M.A.H., and Drob, D., 2010, Atmospheric variability and infrasound monitoring, Global Continuous Infrasound Monitoring for Atmospheric Studies, Springer Geosciences, p475-507.Hedlin, M.A.H. and Alcoverro, B., 2005, The use of impedance matching capillaries for reducing resonance in rosette spatial filters, J. Acoust. Soc. Am, 117, 1880-1888.Hedlin, M.A.H., 2006, Infrasonic Monitoring, 2006 Yearbook of Science and Technology, McGraw-Hill, 163-166.Hedlin, M.A.H., de Groot-Hedlin, C.D. and Walker, K., 2009, Looking up with the USArray, Earthscopeonsite newsletter, winter 2009, p 1,3. Hedlin, M.A.H., Drob, D., Walker, K. and de Groot-Hedlin, C., 2010, A study of acoustic propagation from a large bolide in the atmosphere with a dense seismic network, Journal of Geophysical Research – Solid Earth (in press). Matoza, R.S., Hedlin, M.A.H., Garces, M.A., 2006, An infrasound array study of Mount St Helens, Journalof Volcanology and Geothermal Research. v160, issues 3-4, p249-262. Matoza, R.S., Garces, M.A., Chouet, B.A., D’Auria, L., Hedlin, M.A.H., de Grooth-Hedlin, C.D., Waite, G.P., 2008, The source of infrasound associated with long period events at Mount St. Helens, in review with J. Geophys. Res., 114, B04305, doi:10.1029/2008JB006128.Matoza, R.S., Fee, D., Garces, M.A., Seiner, J.M., Ramon, P.A. and Hedlin, M.A.H, 2009, Infrasonic jet noise from volcanic eruptions, Geophysical Research Letters, v 36, doi:10.1029/2008GL036486. Walker, K., Walker, K. and Hedlin, M.A.H., 2010, A review of infrasound wind noise reduction technologies, GlobalContinuous Infrasound Monitoring for Atmospheric Studies, Springer Geosciences, p141-182.Zumberge, M., Hedlin, M.A.H., and Shearer, P., .., 2007, Methodologies for determining infrasound phase velocity direction with an array of directional acoustic sensors, J. Acoust. Soc. Am. 124, 2090-2099.

David R. Hilton

Professor of Geochemistry



Research Interests: Noble gas and major volatile isotope geochemistry of subduction zones, mantle hotspots, groundwaters and geothermal systems.

We continue to investigate the volatile systematics of various tectonic environments. New publications this year include work on convergent margins – the Mariana Islands and Central America – as well as mantle hotspots – Iceland and near-ridge seamounts in the Pacific.

The Mariana Islands were formed in response to subduction of the Pacific Plate under the Philippine Plate. The island volcano of Anatahan erupted for the first time in the historical record in 2003, and we formed part of the NSF-MARGINS rapid response team sent out to collect samples. The publication by De Moor et al. (2010) presents sulfur isotope data for ash and pumice from different stage of that new eruption. The data are used to model the progressive evolution of the magma reservoir as degassing depleted the source in volatiles. The study by Mitchell et al. (2010) considered volcanic and hydrothermal gas chemistry and nitrogen isotope systematics from a total of 8 islands throughout the entire Izu-Bonin-Mariana (IBM) volcanic chain, and tackled issues of nitrogen sources, fluxes and mass balance, i.e. input via the trench versus output along the volcanic front. Macpherson et al. (2010) considered the flux of carbon along the Mariana Trough – the back-arc spreading axis behind the volcanic front. They concluded that there was no evidence for slab-related carbon loss via the back-arc, implying that the bulk of the CO2 subducted into the mantle at the trench was lost either via the volcanic front or carried into the deeper mantle, beyond the zone of arc magma generation.

On-going studies in Central America have considered three aspects of the fluid and volatile cycle at this convergent margin. First, Tyron et al., (2010) and Füri et al., (2010a), respectively, looked at the fluid and carbon chemistry of submarine cold seeps located on the Costa Rica fore-arc. The objectives were to (a) ascertain the origin of the fluids and the processes controlling their composition – serpentinization from the former study, and (b) the relative flux of CO2 emitted via the fore-arc – negligible compared to the volcanic front in the latter paper. Second, Barnes et al. (2009) analyzed ash, tephra and lavas from throughout Central America for chlorine isotopes, and found large variations to exist only in the central segment of the volcanic front (Nicaragua). This observation was interpreted as evidence of serpentinization – sediment admixture in a region of the subduction zone where hydration of the down-going plate is extensive. Finally, Hilton et al. (2010) reported He and CO2 results from a 9-year monitoring program of 2 active volcanoes in Costa Rica – Poas and Turrialba. Variations in isotopic compositions and relative abundances of these two volatiles were ascribed to increased mantle-crust interaction and degassing of new magma batches.

Our research in mantle geochemistry continued with the publication of Füri et al. (2010b) which reported He-Ne-Ar isotope data from both the neovolcanic zones and older regions of the Icelandic crust. We concluded that melt depletion, melt mixing, degassing fractionation and air interaction all contribute to the observed isotopic variations: however, it was still possible to discern regional differences in the characteristics of the Iceland mantle with more primitive contributions prevalent in central and southern Iceland. In a related study, Hahm et al. (2009) analysed near-ridge seamounts from the Pacific to consider the mantle origin of high 3He/4He ratios. It was shown that coupled He and radiogenic isotope data were not compatible with the idea that the upper mantle has dispersed heterogeneous lithologies: rather, the source of the high 3He/4He was likely the deeper (lower) mantle.

New Publications

Hahm, D., Castillo, P.R. and Hilton, D.R. (2009) A deep mantle source of high 3He/4He ocean island basalts (OIB) inferred from Pacific near-ridge seamounts. Geophys. Res. Lett. 36, L20316, doi:10.1029/2009GL040560 (5 pages).

Barnes, J.D., Sharp, Z.D., Fischer, T.P., Hilton, D.R. and Carr, M.J. (2009) Chlorine isotope variations along the Central American volcanic front and back arc. Geochemistry, Geophysics, Geosystems 10, Q11S17, doi:10.1029/2009GC002587 (17 pages).

Mitchell, E.C., Fischer, T.P., Hilton, D.R., Hauri, E.H., Shaw, A.M., de Moor, J. M., Sharp, Z.D. and Kazahaya, K. (2010) Nitrogen sources and recycling at subduction zones: Insights from the Izu-Bonin-Mariana Arc. Geochem. Geophys. Geosyst., 11, Q02X11, doi:10.1029/2009GC002783 (24 pages).

Tryon, M.D., Wheat, C.G. and Hilton, D.R. (2010) Fluid sources and pathways of the Costa Rica erosional convergent margin. Geochem. Geophys. Geosyst., 11, Q04S22, doi:10.1029/2009GC002818 (15 pages).

Füri, E., Hilton, D.R., Tryon, M.D., Brown, K.M., McMurtry, G.M., Brückmann, W. and Wheat, C. G. (2010a) Carbon release from submarine seeps at the Costa Rica fore-arc: Implications for the volatile cycle at the Central America convergent margin. G-cubed 11, Q04S21, doi:10.1029/2009GC002810 (18 pages).

Füri, E., Hilton, D.R., Halldorsson, S.A., Barry, P.H., Hahm, D., Fischer, T.P. and Gronvold, K. (2010b) Apparent decoupling of the He and Ne isotope systematics of the Icelandic mantle: the role of He depletion, melt mixing, degassing fractionation and air interaction. Geochim. Cosmochim. Acta. 74 pp 3307-3332.

Hilton, D.R., Ramirez, C.J., Mora-Amador, R., Fischer, T.P., Füri, E., Barry, P.H. and Shaw, A.M. (2010) Monitoring of temporal and spatial variations in fumarole helium and carbon dioxide characteristics at Poas and Turrialba volcanoes, Costa Rica (2001-2009). Geochemical Journal 44, (In Press).

De Moor, J.M., Fischer, T.P., Sharp, Z.D., Hauri, E., Hilton, D.R. and Atudorei, V. (2010) Sulfur isotope fractionation during the May 2003 eruption of Anatahan volcano, Mariana Islands: Implications for sulfur sources and plume processes. Geochim. Cosmochim. Acta 74 pp 5382-5397.

Macpherson, C. G., D. R. Hilton, and K. Hammerschmidt (2010) No slab-derived CO2 in Mariana Trough back-arc basalts: Implications for carbon subduction and for temporary storage of CO2 beneath slow spreading ridges, Geochem. Geophys. Geosyst., 11, doi:10.1029/2010GC003293.

Glenn IerleyProfessorEmail: [email protected]: 4-5917

Research interests: turbulence, applied mathematics

This year saw a continuation of collaboration with my former postdoc Phil Livermore(now in a permanent post at Leeds) and Andy Jackson (ETH) as we used the analytic toolsdeveloped over the past several years (the latest of which are noted in the publications listedbelow) to devise a suitable time-stepping scheme for a model of the Earth’s magnetic field.

The preeminent problem in nearly all numerical simulations of geophysical processes isour inability to resolve all the dynamically significant space and time scales of motionthat the governing parameters warrant. This is especially acute for the geodynamo, wherethe dimensionless measure of viscosity of the liquid iron core is of order 10−15. Largesimulations that consume many hours on the world’s fastest supercomputers (e.g. Japan’sEarth Simulator) may get us down to 10−6 or so but, for want of a rigorous theory, it is notpossible to say whether computations in that range are substantially similar to the resultsthat would obtain at the smaller value.

Owing to the extreme delicacy of one particular balance, the so-called “Taylor constraint”that is expected to be operative in the geodynamo, one can reasonably doubt that 10−6 is yetsufficiently small, although those calculations do broadly suggest the increasing relevanceof the constraint. So it is of considerable interest to find alternate, and more important,independent means to characterize how the dynamical balance might operate in the limitthat the viscosity tends to zero in order to have an end point of comparison.

The magnetic and velocity fields in the Earth’s core obey the “pre-Maxwell” and NavierStokes equations respectively. On the assumption that the field must at every instantsatisfy the “Taylor constraint”, we find using the tools noted above that the evolution mustfollow a specially restricted version of these equations. It is our capacity to describe thatrestriction explicitly (as a sequence of dozens to hundreds of nonlinear constraints) as wellas having a particularly efficient numerical representation of the fields that leads naturallyto a time-stepping scheme. In conceptual terms, one can imagine that the evolution of thegeodynamo absent any constraints corresponds to the motion of a point in three dimensions,whose instantaneous time rate of change depends on position in that space. The addition ofthe constraint can be thought of as a requirement that the squares of the three coordinatessum to unity, that is, x2 + y2 + z2 = 1. So the solution we seek is one that lies of thesurface of a sphere, rather than a trajectory visiting arbitrary points in the space. At agiven point on the sphere, representing an initial condition of the system, the instantaneousrate of change obtained from the unconstrained equations is a vector that, in general, willpoint partly away from the sphere and partly parallel to it (parallel meaning lying in the“tangent plane”). For the constraint to continue to hold, we must keep only the parallelcomponent, and then the point representing the state of the system will continue to tracea pattern confined to the surface of the sphere.

As Taylor noted, in principle this process of discarding the perpendicular component isautomatically achieved if we simply compute a particular portion of the velocity field, the

geostrophic flow. Taylor’s work dates to the early 60s and what was inviting about itwas that one did not need to have any characterization of the machinery for parallel andperpendicular components, which was in any case not available. But, while formally true,numerically Taylor’s prescription alone leads inevitably to disaster owing to exponentialgrowth of error.

We have shown that turning instead to our geometric approach to maintain the evolutionon the equivalent of that elementary example of the sphere is stable.1 This is key. It meansthat we can meaningfully address the question of how magnetic and velocity fields wouldevolve in the absence of any viscosity at all. It may seem curious that this should be feasiblewhen the largest supercomputers in the world can barely hit 10−6. The reason for that isthat we propose to solve the problem not for 10−15 but for zero identically and this letsus simplify the fluid mechanics in a significant way with major implications for numerics.Again for want of rigorous theory, one cannot be certain that the result at zero must begenerally similar to that at 10−15. But that is our conjecture, along with the belief thatTaylor’s constraint must hold.

While these ideas are at one level easy enough to describe, understandably there is muchwork required for their practical implementation as efficient verified code. But that is not all.Beyond the Taylor constraint, one further one is known, identified by Rainer Hollerbach andMichael Proctor. It too must go into this mix. But Phil Livermore has recently identifiedseveral more and we are still grappling with this enriched spectrum of constraints since theyraise certain technical issues that are quite subtle.

It may emerge that results at zero do not differ significantly from those at 10−6 for a rangeof particular geodynamo models. If so, that is good news for the most ambitious modelsand lessens the pressure to focus exclusively on progressive decrease in the (dimensionless)viscosity and allows one instead to explore other parts of parameter space, necessary owingto present uncertainties in other aspects of the geodynamo. But it may well happen theresults differ qualitatively. Then we face a far more formidable challenge for the future,perhaps foremost the theoretical one of understanding the limiting process that connectsone to the other.


Livermore, P., Ierley, G. R., and Jackson, A., The construction of exact Taylor states. II:The influence of an inner core, Phys. Earth Planet. Int., v 178, 16-26, 2010

Livermore, P, and Ierley, G. R., Quasi Lp norm orthogonal Galerkin expansions in sums ofJacobi polynomials, Num. Alg., v 54(4), 533-569, 2010. doi:10.1007/s11075-009-9353-5

1As described in a recent submission to GJI, with our revised version just returned to the referees.

Miriam Kastner

Distinguished Professor of Earth Sciences



Research Interests over the years: Marine geochemistry with focus on: the role and fluxes of fluids in continental margins and ridge flanks including long-term monitoring of fluid chemistry and fluxes and their contribution to oceanic budgets; marine gas hydrates and implications for slope stability and climate change; chemical paleoceanography and oceanic minerals, utilizing existing proxies for paleo-seawater chemistry and establishing new minerals as proxies; sediment geochemistry and diagenesis with emphasis on marine authigenic minerals (i.e., phosphates, silicates, carbonates…).

Most recent focus reflected in the attached publications: On quantifying the marine geological flux of the greenhouse gas methane to the atmosphere, with an emphasis on ocean margins where hydrocarbon seeps are widespread. The natural seeps consist of dead 14C which impacts the ICPP calculations on the anthropogenic input into the atmosphere; all dead 14C input into the atmosphere is subscribed by the ICPP to anthropogenic sources. In the recent past, the prime field study area was the Gulf of Mexico, with a potential to expanding to the Pacific NW and/or offshore Alaska. In the Gulf of Mexico so far more than 3500 deepwater hydrocarbon seeps have been identified. As yet, it is, however, unknown what fraction of the methane in these seeps reaches the atmosphere.

Closely related is the emphasis on fluid cycling in subduction zones, on the subsurfacehydrology, its impact on ocean chemical and isotopic compositions, for example on the Ba, Cl and Cl stable isotope budgets in the ocean, on the associated biogeochemistry, and probably on earthquakes cycles. The research involves seagoing expeditions and in situ short and long-range monitoring of fluid flow and solute fluxes, as well as analytical and experimental work.

The above research is intimately related to research on gas hydrates that focuses on the distribution and abundance of methane hydrates in these tectonic settings, hence, on the role of the lithology and subsurface hydrology on its distribution. This has direct implications regarding concerns about the impact of global change on slope stability, and on the inter-relations between global warming and methane hydrates stability, especially in the permafrost.

It took a number of years to establish that the highly stable mineral marine barite can be used reliably for high-resolution chemical paleoceanographic research. This was accomplished with a former graduate student and post doctoral fellow A. Paytan. We showed that marine barite can be utilized for example, for characterizing the seawater Sr isotopes record, for studies of sedimentation rates, paleoproductivity, and seawater sulfate S isotopes over the past 65 million years. Most recently we extended the S isotopes research to 65-130 Ma, with emphasis on the implications for the relations between the C and S cycles and the evolution of atmospheric oxygen. This highly stable mineral, becomes unstable, dissolves, in subduction zones where sulfate is being reduced. Some of the dissolved barite-Ba cycles through arc volcanoes, and may be used to estimate sediment recycling in subduction zones. Furthermore, the distribution of barite and dissolved Ba in the sediment pore fluids, in the sulfate reduction zone and below it, may be used as a proxy for the history of the depth distribution of the important sulfate-methane redox transition zone, that is the upper boundary of marine gas hydrate occurrence in the subsurface.

Relevant Recent Publications

Schrum, H.N., Spivack, A.J., Kastner, M., D’Hondt, S., 2009, Sulfate-reducing ammonium oxidation: A thermodynamically feasible metabolic pathway in subseafloor sediment. Geology, Oct. 2009.

Solomon, E.A., Kastner, M., and MacDonald, I.R., 2009,Considerable methane fluxes to the atmosphere from hydrocarbon plumes in the Gulf of Mexico, Nature Geoscience, doi:10.1038/NGEO574.

Solomon, EA, Kastner,M., Wheat, C. G., Jannasch, H., Robertson, G., Davis, E.E., Morris, J.D., 2009, Long-term hydrogeochemical records in the oceanic basement and forearc prism at the Costa Rica subduction zone, Earth Planet. Sci. Letters, 282 (1-4) 240-251.

Torres, M.E., and Kastner, M., 2009, Clues about carbon cycling in methane-bearing sediments using stable isotopes of the dissolved inorganic carbon, IODP Expedition 311: Data Report. Proceed. IODP Scientific Results, 311, doi:10.2204/iodp.proc.311.206.2009.

Kastner ,M., Claypool, G., and Robertson, G., 2008, Geochemical constraints on the origin of pore fluids gas hydrate distribution at Atwater Valley and Keathley Canyon, Northern Gulf of Mexico. Marine and Petroleum Geology, 25, 860-872.

Kastner, M., Torres, M., Solomon, E., and Spivack, A.J., 2008, Marine pore fluid profiles of dissolved Sulfate; do they reflect in situ methane fluxes? Fire in the Ice, DOE, Summer 2008: 6-8.

Kastner, M., Spivack, A.J., Torres, M., Solomon, E., Borole,, D.V., Robertson, G.A., and Das, H.C., 2008, Gas hydrates in three Indian Ocean regions, a comparative study of occurrence and subsurface Hydrology. Proceed. 6th Interntl. Conf. on Gas Hydrates (ICGH 2008), Vancouver, BC, Canada, 1-6.

Malinverno, A. Kastner, M., Torres, M.E., and Wortmann, U.G., 2008, Gas hydrate saturation from pore water chlorinity and downhole logs in a transect across the northern Cascadia margin (Integrated Ocean Drilling Program Expedition 311), J. Geophys. Res., 113: B08103, doi: 10.1029/2008JB005702.

Newman, K.R., Cormier, M-H., Weissel, J.K., Driscoll, N.W., Kastner, M., Solomon, E.A., Robertson, G. Hill, J.C., Singh, H. Camilli, R., and Eustice, R., 2008, Active methane venting observed at giant seafloor pockmarks along the U.S. mid-Atlantic shelf break. Earth Planet. Sci. Letters, 267: 341-352.

Solomon, E.A., Kastner, M., Jannasch, H., Robertson, G., and Weinstein, Y., 2008, Dynamic fluid flow and chemical fluxes associated with a seafloor gas hydrate deposit on the northern Gulf of Mexico slope. Earth Planet. Sci. Letters, 270, 95-105.

Torres, M.E., Tréhu, A.M., Cespedes, N., Kastner, M., Wortmann, U.G., Kim, J-H., Long, P., Malinvero, A., Pohlman, J.W., Riedel, M., and Collet, T., 2008, Methane hydrate formation in Turbidite sediments of northern Cascadia, IODP Expedition 311, Earth Planet. Sci. Letters, 271: 170-180.

Wei, W., Kastner, M., and Spivack, A., 2008, Chlorine stable isotopes and halogen concentrations in convergent margins with implications for the Cl isotopes cycle in the ocean. Earth Planet. Sci. Letters, 266: 90-104.

Kastner, M., Becker, K., Davis, E.E., Fisher, A.T., Jamnasch, H.W., Solomon, E.A., and Wheat, G., 2006, New insights into the hydrogeology of the ocean crust through long-term monitoring, Oceanography, 19: 46-57.

Solomon, E., Kastner, M., Robertson, G., 2006, Barium cycling at the Costa Rica convergent margin, Data Report, Proceed. ODP Scientific Results, 205, 205, 1-22.

Paytan ,A., Kastner, M., Campbell, D., and Thiemens, M.H., 2004, Seawater sulfur isotope fluctuations in the Cretaceous. Science, 304, 1663-1665.

Kerry Key Assistant Research Geophysicist Email: [email protected], Web: http://marineemlab.ucsd.edu/kkey Phone: 22975 Research Interests: Marine electromagnetic exploration of subduction zones, mid-ocean ridges and the continental shelves, hydrocarbon exploration, numerical methods for electromagnetic modeling, marine geophysical instrumentation.

SERPENT: Serpentinite, Extension and Regional Porosity Experiment across the Nicaraguan Trench: This NSF funded project uses electromagnetic (EM) exploration techniques to study the fluid content of the subducting oceanic plate offshore Nicaragua and was funded in collaboration with Steven Constable (IGPP/SIO) and Rob Evans and Dan Lizarralde (Woods Hole Oceanographic Institution). The month-long research cruise for this project took place in April-May this year aboard the R/V Melville and was my first big cruise as Chief Scientist. We collected 54 stations of marine magnetotelluric (MT) data and deep-towed nearly 800 km of controlled-source electromagnetic (CSEM) data (Figure 1). This is a huge milestone for marine EM as our project’s size far exceeds previous MT surveys of subduction zones, and is the first CSEM survey of a subduction zone. We now have a huge volume of marine EM data, from which we will learn a great deal about the nature of cracking, extension, porosity and serpentinization of the oceanic lithosphere as it is subducted beneath the continental margin. This data will provide constraints on the amount of water entering the subduction system and allow us to study its implications for seismicity and the onshore volcanic system.

Figure 1. Marine EM survey of the subduction zone offshore the west coast of Nicaragua. Blue dots show the location of 54 marine EM receivers deployed across the deep-ocean, the Middle America Trench and up the continental slope. Green circles show circular CSEM tows used to constrain anisotropic conductivity before (left) and after (right) reactivation of normal faults associated with the bending of the oceanic plate.

Interpretting vector marine CSEM data with an unknown orientation: Marine CSEM data is now routinely collected on the continental shelves for offshore oil and gas exploration. In some cases, the seafloor electric and magnetic field recordings have unknown orientations due to the absence of magnetic compass and tilt data. Key and Lockwood (2010) considers the practical case of how to best interpret this data, showing that the orthogonal Procrustes rotation method that is commonly applied for image analysis can also be used to solve for the sensor orientations. This is accomplished by coupling the Procrustes method into a non-linear inversion method that iteratively solves for the unknown sensor orientations and the seafloor conductivity (Figure 2).

Review of Marine EM: In September 2010 I presented an invited review paper on “Marine electromagnetic studies of seafloor resources and tectonics” at the 20th International Workshop on Electromagnetic Induction in the Earth, held in Giza, Egypt. My charge was to cover interesting developments in marine EM since previous reviews were given in 2004. As shown in Figure 3, the dramatic increase in the publication rate after 2004, associated with the rapid industrial uptake of marine EM methods, gave me no shortage of material to cover.

Recent Publications Myer D., S. Constable, and K. Key (2010), A marine EM survey of the Scarborough gas

field, Northwest Shelf of Australia, First Break, 28, 77–82. Key K. and A. Lockwood (2010), Determining the orientation of marine CSEM receivers

using orthogonal Procrustes rotation analysis, Geophysics, 75, F63–F70.

Figure 2. Left: Map view of the electric field strength (colors) and polarization ellipses for a transmitterlocated off (a) and over (b) a resistive 2D hydrocarbon reservoir. Right: resistivity-depth profile obtainedfrom non-linear inversion (smooth and cut) of CSEM data collected over the Pluto gas field offshoreAustralia, obtained while jointly applying the Procrustes method to estimate the unknown sensororientations. The gray line shows resistivity measured in an exploration well located 40 km away.

Cumulative number ofpeer-reviewed papers published onmarine electromagnetic methodssince early work in the 1960’s. Theincrease in the publication rate in2004 onward is associated with theindustrial adoption of marine EMmethods for offshore hydrocarbonexploration.

Deborah Lyman Kilb

Associate Project Scientist

Email address: [email protected] extension: 2-4607

Research Interests: Crustal seismology, earthquake triggering, earthquake source physics.

Deborah Kilb’s current research areas include crustal seismology and earthquake source physics, with an emphasis on understanding how one earthquake can influence another.

Potential triggers for large ruptures along the southern San Andreas Fault: In a collaborative project with graduate students Daniel Brothers and Karen Luttrell, in addition to professors Neal Driscoll and Graham Kent, Kilb explores why the southern San Andreas Fault (SSAF) in California has not had a large earthquake in approximately 300 years, yet the average recurrence for the previous five ruptures is about 180 years. Key in this work is the observation that a 60 km section of the SSAF has periodically been submerged during high lake levels of the large late-Holocene Lake Cahuilla (LC), and emerging evidence indicates coincident timing between LC flooding and fault displacement. As a large SSAF earthquake appears imminent, it is important to understand how crustal stress perturbations can promote or inhibit fault failure(s) in this region. In this work, Kilb and co-workers assess the potential for LC to act as a catalyst in triggering a sequence of large earthquakes. They find calculated static stress perturbations from LC flooding and/or rupture of secondary faults beneath LC are sufficient (i.e., reaching levels above an assumed triggering threshold of 0.1 MPa) to potentially trigger large earthquakes on the SSAF. Since the current lake level is relatively stable, any future interaction between the faults under today’s Salton Sea and the SSAF will depend solely on tectonic loading, without any perturbing stresses

Figure 1. Map of Coulomb static stress change. StaticCoulomb stresses at a depth of 4 km generated by rupture of an extensional fault (green line shows surface trace; red rectangle shows the extrapolated fault plane; black line shows the calculation depth) embedded in an elastic half-space, using a friction coefficient of 0.6. The simulation applies 1.0 m of normal displacement to a 65°SE dipping plane that is 15 km long and 8 km deep. Resulting stresses are derived on fault planes oriented similar to the SSAF (strike=325°; dip=90°; rake=180°). Warm colors indicate areas where failure is promoted and cool colors where failure is inhibited. Stress lobes are saturated at ±0.6 MPa.

from lake level changes. In general, these results highlight the importance of including lake loading and secondary fault ruptures in seismic hazard assessments, as both have the potential to modulate earthquake cycles on major plate boundary faults such as the SSAF (Brothers et al., In Review).

A Case Study of Two Magnitude ~5 Mainshocks In Anza, California: Is The Footprint of an Aftershock Sequence Larger than We Think? It has been traditionally held that aftershocks occur within one to two fault lengths of the causative mainshock. Kilb’s work with Karen Felzer (USGS) demonstrates that this perception has been shaped by the sensitivity of seismic networks. The 2001 and 2005 magnitude ~5.0 earthquakes near Anza in southern California occurred in the middle of the densely instrumented ANZA seismic network and were unusually well recorded. Examining these data Kilb and Felzer find that, for both sequences, the decay of aftershock density with distance is similar to those observed elsewhere in California. This indicates there is no need for any additional triggering mechanisms and suggests that given widespread dense instrumentation, aftershock sequences would routinely have footprints much larger than currently expected (Felzer & Kilb, 2009).

Cyberinfrastructure Enabled Science Learning: This year, Kilb was the seismology domain expert for two different projects related to improving science learning. Collaborations with a Chicago based group created the “RoomQuake” project, in which the student’s classroom becomes an active seismic field (Moher et al., 2010). This project includes simulated seismographs depicting continuous strip-chart seismic recordings, which are located in three different locations of the classroom. Most of the time, the seismograms reflect a low level of background vibration. At (apparently) unpredictable times, a crescendoing rumble emanating from a subwoofer signals the occurrence of an earthquake. Upon hearing this signal students move to the seismic stations to assess the data, identify P- and S-wave arrival times, and in turn determine the earthquake epicenter and magnitude. The teacher hangs a sized and color-coded (representing magnitude) Styrofoam ball from the ceiling at the epicenter location. Over the course of about two-dozen earthquakes spread over six weeks, a classroom "fault line" emerges. In a different study collaborating with a CSSM group, Kilb assisted in the creation of a web-based interactive earthquake location tool. This Flash-based Earthquake Location Tool (FELT) allows its user to perform computations and interact with Google Maps API as it loads data, images and audios asynchronously, and redraws sections of the screen, all independent of the server with which it is connected. FELT retrieves seismic data for select recent earthquakes from the IRIS databank and displays seismograms that students can interact with to determine an earthquake’s epicenter (Ouyang et al., 2009; to access to the tool and other resources see http://www.csusm.edu/cyberteam/resources/TechQ1Modified.html#tq1).

See http://eqinfo.ucsd.edu/~dkilb/current.html for an expanded description of these projects.

Recent Publications Brothers, D., D. Kilb, K. Luttrell, N. Driscoll and G. Kent, Potential triggers for large ruptures

along the southern San Andreas Fault, in Review, 2010.

Felzer, K. & D. Kilb, A Case Study of Two M 5 Mainshocks In Anza, California: Is The Footprint Of An Aftershock Sequence Larger Than We Think?, Bull. Seism. Soc. Am., doi:10.1785/0120080268, 2009.

Moher, T., J. Wiley, A. Jaeger, B. L. Silva, F. Novellis, D. Kilb, Spatial and Temporal Embedding for Science Inquiry: An Empirical Study of Student Learning, Proceedings of the 9th International Conference of the Learning Sciences (ICLS'10), International Society of the Learning Sciences, 2010.

Ouyang, Y., Lehmann, M., Hayden, K., and Kilb, D., Opportunities Presented when Developing Learning Resources for Middle Schoolers, The Journal of Computing Sciences in Colleges,24:04, p 144 – 150, 2009.

Devendra Lal

Professor of Nuclear Geophysics and Planetary Physics

E-Mail address: [email protected]

Phone Extensions: 4-2134, and 2-2920

Research interests: 1. Utilization of natural nuclear processes to understand planetary physical and chemical processes and their rate constants. 2. Cosmic ray-produced radioisotopes in diverse terrestrial environments, atmosphere, lakes, oceans, and sediments, and of nuclear tracks in moon, meteorites, and terrestrial samples, to understand planetary processes and their rates. 3. Development of quantitative methods for the study of process geomorphology including continental weathering and erosion processes, evolutionary history of diamonds, and phosphorus biodynamics in oceans using cosmogenic 32P, 33P, and 7Be radionuclides. 4. Studies of solar activity in the past <35,000 years based on studies of in-situ cosmogenic 14C in polar ice. 5. Studies of nuclear reactions in the solar photosphere from examination of radionuclides 10Be, 14C, 26Al and 36Cl in solar wind. 6. Studies of past accumulation and ablation rates of polar ice using in situ produced cosmogenic 14C.

Bacterial activity in formation of ironstones: Pebble-sized sandstone concretions, cemented by iron and manganese oxides (iron stones), are found in several sites in southern California. The iron stones exhibit appreciable enrichments of Mn, Zn, Mg, Ti, Fe, U and Th, and fossil bacteria. Cosmogenic 10Be concentrations, in the range of 108 1010 atoms/g, are an excellent indicator of precipitation amounts. Our data favor the model that the iron stones formed within sandy beach ridges during wetter climates following dry climates during which aeolian sediment was added to the beach ridges. Iron, Mn, Zn and other trace element-rich leachates from the dust layers nurtured accelerated bacterial activity in the beach ridges down to depths of a few meters.

Our observations of trace-element enrichments and bacterial fossils underscore the fact that the iron stones are principally a product of bacterial activity. The extreme alternating dry/wet climatic conditions which existed in the past in southern California led to the formation of iron stone concretions within the ancient beach ridges; the time periods represented by the iron stones from the six sites presumably cover the past ~ 1 my. The recent surface explorations on the surface of Mars by the rovers SPIRIT and OPPORTUNITY (cf. Squyres et al. 2006.), showed that similar to southern California, extreme climatic conditions existed on Mars in its early history. It therefore seems that studies of iron stones may provide useful clues to the evolution of soils on Mars in such extreme climates, and possibly even provide criteria to evaluate whether any bacterial activity was present at that time.

Assessing paleo-concentrations of nutrients, C, N and P in global oceans: We obtained data on dissolved trace element concentrations of Fe, Mn, Zn, Al and Ti in surface waters during 140 kyrs B.P., basing on analyses of opaline frustules in two cores on either side of Antarctic Polar Front (APF). The basis of this research rests on our recent discovery that the marine biogenic opal incorporates (Lal et al., 2006) a large number of dissolved elements in its skeleton. We also present a robust method of estimating past diatom productivity. Estimated productivity indices of bioreactive elements, Fe, Mn and Zn increase non-linearly with their increased natural aeolian fluxes (Fig. 1); their fluxes are deduced from observed concentrations of Ti in opal. Several episodes of high Ti fluxes throughout the past 140 kyrs are correlated with Heinrich events. High Al concentrations in diatoms in the two cores at levels comparable to bioreactive Fe suggest a strong catalytic role of Al in diatom productivity.

Solar activity in the past 32,000 years: Measurements of in-situ produced 14C in Greenland samples from the Summit allowed us to determine past solar activity levels, irrespective of changes in the past geomagnetic field intensity or climate. Our studies show that the Sun may have remained in a quiescent period of very low activity during 8500-9500 B.P. and 27,000-32,000 y B.P., similar to that observed during the Maunder Minimum (1645-1675 AD; Eddy, 1988), but for periods longer than that during the Maunder Minimum. We have now extended these studies to studies of an ice core from South Pole in the past 1000 years to measure the magnitude of solar activity. The results agree with historical evidence in several cases but do not support the dates for the Maunder Minimum. We have requested for new ice core from South Pole to check on the real dates for the Maunder Minimum.

Recent Publications

Bieber, J. W., Clem, J., Desilets, D., Evenson, P., Lal, D., Lopate, C. and Pyle, R. Long term decline of South Pole neutron rates. J. Geophys. Res. 112, No. A12102- A12111, 2007.

Jull, A. J. T., Lal, D., Taylor, S., Weiler, R., Grimberg, A., Vacher, L., McHargue, L. R., Freeman, S. P. H.. T., Maden, C., Schnabel, C., Finkel, R. C., Kim, K. J. and Marti, K. 3He, 20,21,22Ne, 14C, 10Be, 26Al, and 36Cl in magnetic fractions of cosmic dust from Greenland and Antarctica. Meteoritics and Planetary Sci. 42 (#10), 1831-840, 2007.

Lal, D., Recycling of cosmogenic nuclides after their removal from the atmosphere; special case of appreciable transport of 10Be to polar regions by Aeolian dust. Earth and Planetary Sci. Lett. 264, 177-187, 2007.

Kim, K. J. Lal, D., Englert, P. A. J. and Southon, J. In situ 14C depth profile of subsurface vein quartz samples from Macraes Flat New Zealand. Nucl. Instr. and Methods Physics Res. B 259, 632-636, 2007.

Lal, D., Cosmic ray interactions in minerals. Encyclopedia of Quaternary Science. Elsevier, Oxford, pp. 419-436, 2007.

Lal, D. and S. Krishnaswami. Cosmic Ray Geophysics : Its evolution in India and its present status. (Submitted, 2005; in press, 2008)

Krishnaswami, S. and Lal, D., Cosmogenic nuclides in the environment: A brief review of their applications, in Recent Advances in Earth System Sciences (eds. H. Gupta and Fareeduddin), Geol. Soc. India, 559 (2008).

Lal, D., and Krishnaswami, S., Cosmic Ray Geophysics: Its evolution in India and its present status in ‘India in the World of Physics: Then and Now' (ed. A. N. Mitra), PHISPC Centre for studies in Civilizations, Pearson Longman, 461 (2009)

Lal, D., Schopf, J. W., Aboott, P.L., Vacher, L., Jull, A. J. T. and McHargue, L. Nuclear, chemical and biological characterization of formation histories of ironstones from several sites in Southern California: Dominant role of bacterial activity. Earth and Planetary Sci. Letters, 296, 227-234, 2010.

Gabi Laske

Associate Research Geophysicist

Email: [email protected]: 4-8774

Research interests: regional and global surface wave seismology; seismology on the oceanfloor; observation and causes of ocean noise; natural disasters and global change

Gabi Laske’s main research area is the analysis of seismic surface waves and freeoscillations, and the assembly of global and regional models.

Global and regional tomography: Laske’s global surface wave database has providedkey upper mantle information in the quest to define whole mantle structure. Graduatestudent Christine Houser used her data to compile an improved model of mantle shear andcompressional velocity, and bulk sound speed. Laske also collaborates with Masters andcurrent graduate student Zhitu Ma to study the cooling signal of the Pacific plate and tocompile a refined global crustal and lithosphere model. Laske has also been involved in theDESERT project (Dead Sea Rift Transect) to image crustal and mantle structure beneaththe Araba Valley south of the Dead Sea. An important aspect of this research is to find thecause for the uplift of the Arabian Plateau east of the Dead Sea Transform Fault.

The PLUME project: Laske is the lead-PI of the Hawaiian PLUME project (Plume–Lithosphere–Undersea–Mantle Experiment) to study the plumbing system of the Hawaiianhotspot. The project aims to resolve the fundamental question whether a plume or othermechanisms feed Hawaii’s extensive volcanism. PLUME researchers conduct comprehensiveseismic tomographic studies using the unique broadband ocean bottom data collected forPLUME. Before PLUME, observations from stations on the Hawaiian island chain providedincomplete models of only the upper mantle as well as spotty receiver function estimates .The PLUME project includes co-PIs from SIO (Laske, Orcutt), WHOI (Collins, Detrick),U. Hawaii (Wolfe), DTM (Solomon, Hauri) and Yale Univ. (Bercovici). The centerpiece ofthe project is a large broadband OBS network which is augmented by 10 temporary landstations. Occupying a total of over 80 sites and having an aperture of over 1000km, thisexperiment is one of the largest in the world. With two 1-year deployments in 2005 through2007, PLUME has been one of the first large, long-duration deployments of broadbandOSBs.

Both deployments collected nearly 200 earthquakes each, providing excellent az-imuthal coverage. Surface wave dispersion analyses reveal a roughly 30km thick low-velocityanomaly in the lower lithosphere beneath the islands of Hawaii and Maui that may tracethe supply route of Hawaii’s magma (Figures 1 and 2). This low-velocity body is associatedwith a marked temperature anomaly of roughly 250◦C and very likely contains melt pock-ets on the order of 2%. The PLUME crustal receiver function study (Leahy et al., 2010)shows extensive crustal underplating beneath the Hawaiian Swell, thereby supporting theanomalies imaged by the surface waves. SWELL, a pilot study leading into the PLUMEproject, showed conclusively that the Hawaiian lithosphere has undergone a thermal reju-venation process with no extensive mechanical erosion and the results from the PLUMEproject confirm this. A pronounced low-velocity feature in the PLUME surface wave modelis imaged in the asthenosphere to the west of Hawaii, documenting that the magma supplycannot come from a straight conduit located southeast of Hawaii as conventional modelssuggested. The PLUME body wave tomography (Wolfe et al., 2009) reveals that the lowvelocity body penetrates into the lower mantle thereby lending strong support that Hawaii’svolcanism is fed by a deep-rooted mantle plume rather than from passive magmatism that

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POHAKIPprof-sw KCCHKCCH

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Distance from Origin [km]Distance from Origin [km]

Figure 2: Cross sections through the Vs model,now displayed as absolute velocities. The locationsof the sections are marked in Figure 1. Structurenear the ends of the profiles is poorly resolved andtherefore has been shaded over. The projectionsof stations POHA, KIP, and KCCH on the islandsof Hawaii, Oahu, and Kauai onto the sections arealso marked.

results from a cracking plate. Tomography also shows that the plume undergoes markedundulations in the mantle wind that is generated by global convection. Graduate studentPaula Chojnacki currently conducts a detailed study of surface wave azimuthal anisotropyto constrain patterns of mantle flow and fabric.


Leahy, G.M., Collins, J.A., Wolfe, C.J., Laske, G, Solomon, S.C. Underplating of theHawaiian Swell: evidence from teleseismic receiver functions, Geophys. J. Int., 183,313–329, DOI: 10.1111/j.1365-246X.2010.04720.x, 2010.

Laske, G., Collins, J.A., Wolfe, C.J., Solomon, S.C., Detrick, R.S., Orcutt, J.A., Bercovici,D. and Hauri, E.H., Probing the Hawaiian hot spot with new broadband ocean bottominstruments, EOS Trans. AGU, 90, 362-363, 2009.

Wolfe, C.J., Solomon, S.C., Laske, G., Collins, J.A., Detrick, R.S., Orcutt, J.A., Bercovici,D., Hauri, E.H., Mantle shear-wave velocity structure beneath the Hawaiian hotspot,Science, 326, 1388–1390, doi: 10.1126/science.1180165, 2009.

Laske, G., Weber, M. and the DESERT Working Group. Lithosphere Structure Acrossthe Dead Sea Transform as Constrained by Rayleigh Waves Observed During theDESERT Experiment, Geophys. J. Int., 173, 593-610, 2008.

Guenter W. Lugmair

Research Chemist

E-mail: [email protected]


Alexander Shukolyukov

Project Scientist

E-mail: [email protected]


Research Interests: Origin and evolution of the solar system - isotopic studies on extraterrestrial materials; extinct radionuclides; cosmochronology; nucleosynthesis; impact structures and impact deposits on Earth.

The principal aim of our work is to improve our understanding of the earliest evolutionary period of our solar system (i.e. the first tens of millions of years). We continue to explore its chronology by using mostly short term chronometers (based on extinct radioactive nuclei), the bearing of short-lived nuclei on planetary heating and differentiation, and the addition of 'exotic' nuclei to solar system matter to help constrain models of nucleosynthesis. We have shown that the 53Mn-53Cr system (T½(53Mn) = 3.7 Ma) is a powerful tool to obtain relative ages of meteorite formation and, more general, of early solar system processes with a time resolution of ~1 Ma or less. The use of a precise absolute Pb-Pb age of the angrite NWA 4801 - our new time marker - and the 53Mn/55Mn ratio in this meteorite at the time of its solidification allowed us to map the relative Mn-Cr ages of other meteorites to an absolute time scale. In particular, we dated various classes of chondrites, achondrites, and unusual meteorites, determined the timing of planetary differentiation and other processes within early planetary bodies.

Our main instrument in these investigations is high precision thermal ionization mass spectrometry. In the last year we conducted the study of the unusual meteorite Northwest Africa 5400 (NWA 5400). NWA 5400 is a brachinite-like achondrite meteorite that is remarkable for having an oxygen isotopic composition indistinguishable from that of the Earth and Moon. This work is a continuation of our effort to improve our understanding of the early evolutionary period of the Solar System by applying 53Mn-53Cr systematics to NWA 5400. The other important goal of this work was to determine a characteristic 54Cr/52Cr ratio for this specimen in an attempt to establish a genetic link between this meteorite and other meteorite classes.

It was shown recently that the bulk samples of various meteorite classes (such as eucrites, mesosiderites, angrites, ordinary chondrites and ureilites) have small but resolvable deficits of 54Cr, whereas different types of the carbonaceous chondrites are characterized by variable excesses of 54Cr. The relative abundances of 54Cr in enstatite chondrites are the same as in terrestrial samples.

The measured 53Cr excesses in chromite, silicate portion, and total rock are essentially the same [Figure 1]. This indicates that 53Mn had practically fully decayed at the time of isotopic closure. Thus, only an upper limit for the 53Mn/55Mn ratio at that time can be obtained: 4.23 × 10-8. Using the angrite

NWA 4801 as an absolute time marker (53Mn/55Mn = 0.96 × 10-6 at 4558 Ma ago), we calculate that the Cr isotopes in NWA 5400 equilibrated no earlier than 4541 Ma ago.

We conducted two series of measurements of the relative abundance of 54Cr in NWA 5400. The results show [Figure 1] that within the uncertainties the relative abundance of 54Cr is indistinguishable from the terrestrial value ( (54) = 0), in contrast to all studied meteorites, except enstatite chondrites.

Although the chromium isotope results do not provide more than a maximum formation age for NWA 5400, they do show that this specimen is significantly younger than brachinites. We concluded that NWA 5400 may represent the ultramafic portion of an asteroidal parent body that witnessed similar processing to brachinites, but that evolved more slowly and originated from a compositionally distinct reservoir, yet one with similarities to the planetary feeding zones of the Earth-Moon system.

Another direction of our work is the use of the Cr isotopic composition as a tracer of extraterrestrial material on Earth. Our investigations of the 53Mn-53Cr isotope system during the last decade have shown that all meteorite classes studied so far have relative 53Cr abundances that are clearly different from terrestrial and are characteristic for individual classes of meteorites. Thus, based on measurements of the Cr isotopic composition, we can unambiguously demonstrate an extraterrestrial component in geological samples on Earth that contain a significant proportion of meteoritic Cr. The Cr method was originally used to demonstrate that the Cretaceous/Tertiary boundary layer contains an abundant extraterrestrial component The K/T boundary sediments from Stevns Klint, Denmark, and Caravaca, Spain, have a Cr isotopic signature that is very similar to carbonaceous chondrites. The obtained results were the first isotopic evidence for the cosmic origin of the K/T layer and the type of the impactor. Subsequently, this method was successfully applied to other impact deposits and impact melt samples. In the last year we completed our work on a series of Late Eocene impact deposits. Using the Cr isotopes isotopes and cosmic ray ages together with impact crater and ejecta chemistry we recently proposed that the Brangane asteroid family is a result of the disruption of a large H-chondrite parent body.

Relevant Recent Publications

Shukolyukov A., Lugmair G.W., Day J.M.D., Walker R.J., Rumble D., III, Nakashima D., Nagao K., and Irving A. J. (2010) Constraints on the formation age, highly siderophile element budget and noble gas isotope compositions of Northwest Africa 5400: an ultramafic achondrite with terrestrial isotopic characteristics. In Lunar and Planetary Science XLI, #1492, Lunar and Planetary Institute, Houston.

Kyte F.T., Shukolyukov A., Hildebrand A.R., Lugmair G.W., and Hanova J. (2010) Chromium-Isotopes in Late Eocene Impact Spherules Indicate a Likely Asteroid Belt Provenance Earth Planet. Sci. Letters (in review).

Figure 1. 53Mn-53Cr systematics in NWA 5400 and the relative abundance of 54Cr.

Todd Martz

Assistant Professor



Research Interests: Autonomous chemical sensor development, calibration, and implementation. CO2

chemistry of natural waters, marine biogeochemistry.

The Martz Lab develops autonomous chemical sensors used for studying the marine inorganic carbon cycle and the related biogeochemical processes controlling it. We are currently developing instruments to measure pH, total alkalinity, and dissolved inorganic carbon in the ocean; and we regularly incorporate additional, commercially available sensors for pCO2, oxygen, salinity, temperature, and pressure into deployable sensor packages. As a general design benchmark, we build devices capable of collecting (measuring and storing in memory) a minimum of 10,000 measurements, in order to achieve a 1-year deployment period at a 1-hr sampling frequency. The motivation behind our work is a need to better understand and characterize the spatiotemporal state of the marine physical, chemical, and ecosystem environment. Autonomous sensors now play an increasing role in ocean science by providing continuous, high-resolution time series of ocean properties, observed from a variety of platforms including moorings, volunteer observing ships, profiling floats, gliders, drifters, and AUVs. These observations can help us to constrain key processes in the carbon cycle including diel, seasonal and annual rates of net community production (plant growth/decay), export production (particle sinking), biogenic CaCO3 formation/dissolution, and gas exchange at the air-sea interface. In addition, with further improvements to in-situ sensing technologies we hope to be able to reliably detect long terms trends (> annual) in the ocean, driven by anthropogenic CO2 invasion.

Over the past year, we have received several requests to reproduce autonomous pH sensors now known to many in the oceanographic community as the “SeaFET” and “SeapHOx”. To date we have built 42 sensors for 13 different collaborators. The key element to both of these packages is a modified Honeywell DuraFET® Ion Sensitive Field Effect Transistor (ISFET) pH sensor. This new technology has proven to be extraordinarily robust for unattended in-situ applications where sensors are operated for many months on moorings. Through an active non-disclosure agreement, we are currently working with scientists at Honeywell Labs in an effort to modify the DuraFET for operation on profiling floats.

Efforts are now underway to complete the construction of the Scripps pH Sensor Calibration Facility by early 2011. This facility will be utilized to simultaneously calibrate up to 20 fully-assembled sensors using techniques traceable to SIO’s certified seawater standards for CO2 and pH (the work of Prof. Andrew Dickson). Given SIO’s background as the world’s center for seawater CO2 standards, combined with what is arguably the most successful and accessible autonomous seawater pH sensor developed to date, SIO is poised to lead the world in providing CO2 sensor calibrations for future ocean observation programs ranging from small collaborations to multi-institutional global-scale efforts.

Graduate students in our lab are currently working on new sensor development projects such as a microfluidic “micro-rosette” for operation onboard profiling floats and nanoscale on-chip methods for other CO2 parameters including total dissolved inorganic carbon and total alkalinity.

Initial deployments necessary for testing and ground-truthing these sensors are commonly carried out in local waters. As a result we are now gaining a more comprehensive understanding of coastal pH and oxygen dynamics, as observed by our sensors located on moorings deployed by SIO (Uwe Send and Lisa Levin) at Del Mar, Imperial Beach, the La Jolla Kelp forest, and in the California Current Ecosystem

LTER CalCOFI stations. Such work is necessary for laying a foundation of baseline levels and natural variability in pH and oxygen experienced by organisms that may be sensitive to ocean acidification and de-oxygenation, two processes that have been identified as potential future threats to marine habitats. Further, establishing a robust coastal sensor network is a long standing goal of local, state, and federal agencies interested in early warning systems that could be used to alert local fisheries of strong upwelling signals that may induce negative impacts on sensitive organisms, or used to initiate a strategic sampling campaign in response to an episodic event.


Martz, T., R., J. Connery, G., and K. Johnson, S. 2010. Testing the Honeywell Durafet® for seawater pH applications. Limnology and Oceanography: Methods 8: 172-184.

Byrne, R. M. D. DeGrandpre, T. Short, T. R. Martz, L. Merlivat, C. McNeil and F. Sayles, 2010. Sensors and Systems for Observations of Marine CO2 System Variables. In: J. Hall, D.E. Harrison and D. Stammer (Editors), Proceedings of OceanObs’09: Sustained Ocean Observations and Information for Society ESA Publication WPP-306, Venice, Italy.

Stephen P. Miller

Specialist in Marine Geophysics; Head, Geological Data Center


Phone extension: 858-534-1898

http://gdc.ucsd.edu ; http://ssdb.iodp.org

Research Interests: digital archiving and preservation, marine geophysics, mid-ocean ridges, seafloor mapping, education and outreach.

The Geological Data Center has been in operation for 40 years, carefully archiving and disseminating data from Scripps cruises. In recent years there have been significant advances in online access, as the activities have been extended to a national, and an international level, with long term external funding.

During the last year, the new Rolling Deck to Repository (R2R; http://www.rvdata.us) program has launched operations to migrate shipboard data from the US University-National Oceanographic Laboratory System (UNOLS) and other academic vessels into long term national archives. Catching up with a backlog of cruises mostly from 2009, during the first year a total of more than 5 million data files have been captured, from 1436 cruises on 23 vessels. Much of the complexity is due to the fact that these vessels are managed by 18 different operating institutions. Underway device types include navigation, multibeam, subbottom, gravimeter, magnetics, ADCP, CTD, meteorology, etc. While most underway data will be promptly and publicly released, R2R will securely embargo any specific datasets identified in advance by the chief scientist, for a proprietary hold period of up to two years. Soon after shipboard data are received by R2R, the entire original distribution is safely stored in a deep archive for long-term preservation, and a cataloging process is undertaken to assemble data sets for delivery to National Data Centers. A suite of new R2R standard products will be generated for each cruise including basic cruise metadata, an operations report, and quality controlled navigational products. The approaches, technology and procedures of R2R are being coordinated with activities across NSF and NOAA, including the Ocean Observatories Initiative (OOI), and with European programs such as SeaDataNet, Eurofleets and

Figure 1. Example of recent R/V Roger Revelle cruises being archived by R2R.

GeoSeas. R2R is a close collaboration of researchers and data managers at SIO, the San Diego Supercomputer Center (SDSC), the Lamont-Doherty Earth Observatory (LDEO, Columbia University), the Woods Hole Oceanographic Institution (WHOI), and Florida State University.

Established in 2001, the SIOExplorer Digital Library (http://SIOExplorer.ucsd.edu) has been preserving the complete context of almost all types of data from more than 1000 SIO cruises since the 1950’s, including cruise reports, navigation, underway gravity, magnetics and depth, temperature and current profiles, high resolution meteorology, biological, chemical, dredged rock and sediment core samples, as well as seismic data, multibeam swath bathymetry, maps and seafloor visualization files. SIOExplorer maintains five online collections: Cruises, Photo Archives, EarthRef Seamounts, Marine Geological Samples, and the Educator’s Collection. SIOExplorer was developed with support from the NSF National Science Digital Library program.

The Geological Data Center, in partnership with the SDSC, also operates the Site Survey Data Bank (SSDB; http://ssdb.iodp.org) for the Integrated Ocean Drilling Program (IODP). The SSDB is a science decision support system, built on a digital library, enabling the efforts of international review panels. The SSDB has been in operation since 2005 and now supports 254 proposals and a community of more than 500 proponents and reviewers. It has grown to hold 7867 digital objects, such as seismic sections, bottom photographs, bathymetric maps and background reports. This year a new searchable interface provides information about our pre-2005 archival holdings, prior to the launch of the digital library, including 33,380 physical objects and 13,726 digital files, 6661 drilling sites, and 1141 proposal versions. The SSDB also provides a persistent archive for expedition planning, shipboard drilling operations, and long-term education and outreach.

The activities of the Geological Center are clearly a team effort, benefiting from the efforts of a devoted staff from SIO and the SDSC (Figure 2).

Figure 2. The team of current GDC staff members includes Stephen Miller, Karen Stocks (SDSC), Dru Clark, Aaron Sweeney and Jake Perez.

The GDC functions under the Geosciences Research Division, leveraging partial institutional support with external awards from NSF. Further information is available at http://gdc.ucsd.edu

Jean-Bernard Minster Professor of Geophysics Email address: [email protected] Phone extension: 45650

Research Interests: Plate tectonics and plate deformation; Application of space-geodetic techniques to study crustal dynamics; Satellite laser altimetry and Satellite Synthetic Aperture Radar applications to Earth studies; Earthquake source physics and large-scale supercomputer earthquake simulations; Earthquake prediction, pattern recognition; Multiscale modeling in geophysics & applications of IT technologies—in particular 4D visualizations—to earthquake modeling; Verification of nuclear Test Ban Treaties by geophysical means (seismic, imaging, ionosphere). Application of hyperspectral imaging to paleoseismology. Member of the ICESat science team since 1989.

Recent research: Large-scale simulations of seismic events and seismic wave propagation on super-computers typically generate an enormous volume of output, often in the range of tens of Terabytes. Except to answer very limited, narrow questions where the answer can be expressed in terms of a few numbers, it is impractical to study such output by means other than visualization. This has been used very successfully at the Southern California Earthquake Center to highlight the results of the TeraShake, PetaShake, and CyberShake series of simulations. However, the movies generated have typically been restricted to surface fields. Visualizing the interior of the Earth during a dynamic phenomenon has proved a very difficult task. Research over the past year has focused on visualizing seismic wave fields in the interior of the crust. This was done with Computer Science Graduate Student Emmett McQuinn, in collaboration with San Diego SuperComputer Center researcher Amit Chourasia, and Calit2 researcher Jürgen Schulze.

The approach we adopted was to represent field values (scalar, vector or tensor) at the nodes of a mesh covering the visualization volume, using “glyphs” of various sorts. Glyphs offer a reasonably flexible way to display the fields as a function of time. For instance in the case of vector displacement, velocity or acceleration fields, the glyphs

may be oriented to indicate the vector direction, and size and color may be used to represent the vector magnitude. With complex time-dependent volumetric fields, it is very helpful to minimize the need for elaborate thought processes involved in interpreting the images, so a major part of our effort was aimed at creating as intuitive a display as possible. We have experimented with a wide variety of glyphs. Only a few proved to be adequate for our purpose. One of these is the “comet glyph” rendering of the volumetric velocity field from the TearaShake simulation, shown below.

Relevant Publications Ely, Geoffrey P. Steve M. Day and Jean-Bernard Minster, A support-operator method for

viscoelastic wave modeling in 3-D heterogeneous media, Geophys. J. Int.,doi:10.111/j.1365- 246X.2007.03633.x, 2007

Olsen, K. B., S. M. Day, J. B. Minster, Y. Cui, A. Chourasia, D. Okaya, P. Maechling, and T. Jordan, TeraShake2: Simulation of Mw7.7 earthquakes on the southern San Andreas fault with spontaneous rupture description, Bull. Seism. Soc. Am., 98, doi:10.1785/0120070148, pp. 1162 -1185, 2008

Cui, Y., Moore, R., Olsen, K., Chourasia, A., Maechling, P., Minster, B., Day S., Hu, Y., Zhu J., Majumdar, A. and Jordan, T., 'Enabling Very-Large Scale Earthquake Simulations on Parallel Machines ', Advancing Science and Society through Computation:Lecture Notes in Computer Science series, Springer, (2007): pp. 46-53. 2008

Cui Yifeng, Reagan Moore, Kim Olsen, Amit Chourasia, Philip Maechling, Bernard Minster, Steven Day, Yuanfang Hu, Jing Zhu and Thomas Jordan, Toward Petascale Earthquake Simulations, Acta Geotechnica, doi: 10.1007/s11440-008-0055-2, 2008

McQuinn, Emmett, Visualization of Time-Dependent Seismic Vector Fields With Glyphs, MS. Thesis UCSD, 2010

Walter Munk Research Professor Email address: [email protected] Phone extension: 42877

Research Interests: Physical Oceanography, Ocean Acoustics and Climate.

The year 2010 was dominated by the award of the Crafoord Prize by the Swedish Academy of Sciences for “Lifetime Achievement.” Instead of pontificating about past work, I gave the Award Lecture on some highly risky future plans for research on the global rise in sea level (SLR). Present predictions have 100% uncertainty limits and are almost useless. Arctic and Antarctic glaciers slide down the mountain sides into the sea until they comes off the bottom at the grounding line (GL). The floating ice sheet may extend toward the ice front (IF) for more than 100 km. Lying between the floating ice sheet and sea floor is an ocean cavern, the only piece of ocean never visited by men. Some very recent work suggests that much of the sea level rise is associated with the melting at the bottom of the ice near the GL where it is in contact with relatively warm ocean water. We are proposing monitoring the temperature in the ocean cavern using acoustic methods (references 1 and 2).

By accident the Crafoord Prize award coincided with the publication of my career (3).

I have continued the work on waves in the 1 mm to 1 m scales, straddling the transition from gravity to surface tension (4, 5). These scales have received very little attention as compared to the longer surface waves, yet these are the scales at which momentum is transferred from atmosphere to ocean (wind stress). The incentive for this study came from a recent French compilation of 8 million satellite images of sun glitter. The compilation raises more questions than it answers, hence the title. Significant information concerning the short waves comes (surprisingly) from measurements of pressure on the deep-sea bottom at 5 km depth and measurements of ocean surface slopes from satellites at 500 km elevation.

Relevant Publications 1. Munk, W. (2010) The Sound of Climate Change: Crafoord Prize Scientific Lecture, Tellus,

submitted.2. Dushaw, B.D., P.F. Worcester, W.H. Munk, R.C. Spindel, J.A. Mercer, B.M. Howe, K.

Metzger Jr., T.G. Birdsall, R.K. Andrew, M.A. Dzieciuch, B.D. Cornuelle, and D. Menemenlis (2009). A decade of acoustic thermometry in the North Pacific Ocean. Journal of Geophysical Research, 114, C07021, doi: 10.1029/2008JC005124.

3. von Storch, H. and K. Hasselman (2010) Seventy Years of Exploration in Oceanography: A Prolonged Weekend Discussion. Heidelberg, Germany: Springer, 137 pp.

4. Munk. W. (2009) An Inconvenient Sea-Truth: Spread, Steepness and Skewness of Surface Slopes. Annual Review of Marine Science, 1: 377–415, 10.1146/annurev.marine.010908.163940.

5. Farrell W.E. and Walter Munk (2010). Booms and Busts in the Deep. J. Phys. Oceanography, in press.

6. Munk, W. and C. Pendarvis (2010) Where the Swell Begins. Groundswell Publication Annual Publication, 5, 242-255, in press.

Richard D. Norris

Professor of Paleobiolgy and Paleoclimatology



Research Interests: Large-scale diversification of biodiversity, Paleogene and Cretaceous warm climates, evolutionary and ecosystem dynamics in pelagic organisms.

The past year, my laboratory group has focused on biological evolution, ecology and climate change in the oceans. Dr. Celli Hull graduated with a thesis on the ecological recovery from the Cretaceous-Paleogene mass extinction. The two of us also wrote a review paper on speciation in the oceans and have published our work (with Karen Osborn and MBARI’s Bruce Robison) on the ecologyof mid water foraminifera. My climate studies include work on extreme warm periods in the Paleogene by students, Sandra Kirtland and Johnnie Lyman. Finally, I am working on the evolution of pelagic fishes using the fish tooth record in pelagic carbonates. Two examples of my lab’s work are described below:

Ecological variability and history of coastal communities in the past 15,000 years

During the SIO Cal-Echoes cruise to the Santa Barbara Basin in September 2010, we collected kasten cores and piston cores spanning the past 15,000 years. Although analysis has just begun, we think that we have a nearly continuous record of annual sediment layers through the Holcene (the last 11,500 years). These cores are intended for three major studies. First, we will reconstruct climate variability over the Holocene to see how the predictability of year-to-year climate change affected coastal human societies. Our goal is to test the hypothesis that climate variation plays an important role in the development of California indian social structure. Second, the cores will be used to construct a record of predatory fish population variation over the past ~2000 years. This work, focusing on teeth and collagen mass spectra, will be conducted with NOAA’s Ben Fissel (a former IGERT Ph.D.) and Robert Naviaux (UCSD School of Medicine) and is intended to complement an existing reconstruction of pelagic forage fish populations (sardines and anchovies). Finally, we are also working with Robert Naviaux to extract ‘ancient DNA’ from the cores in order to reconstruct the biodiversity of Holcene and last glacial period marine ecosystems.

Figure 1: Annually-laminated sediment record from the middle of the Santa Barbara Basin. Annual sediment layers are preserved because the low oxygen content of bottom waters prevents large animals from living there and churning up the sediment. The record is interrupted by a few light grey “flood” events. We will use the sediment record (extending back ~15,000 years) to reconstruct climate variability and its impact on California Indians, predatory fish population structure, and extract ‘ancient DNA’ to reconstruct coastal marine biodiversity.

Ecological Recovery of Pelagic Ecosystems after the Cretaceous-Paleogene Mass Extinction

It is well known that export productivity collapsed in the Atlantic for at least 3 million years following the K/Pg mass extinction (65.5 million years ago). However, work with former graduate student, Celli Hull (now a post doc at Yale) and undergraduate Elizabeth Sibert, has found that there was

remarkably little change in total export production in the Pacific. We also find that there was a major turnover in marine plankton after the extinction, with a drastic drop in calcareous nannoplankton production, a massive increase in production of planktonic foraminifera, and little, if any, change n production of fish (as seen in fish teeth and bone). Hence, although there is clear evidence for major changes in parts of the biota in the Pacific, the newly established “disaster” community was able to compensate for the loss of biodiversity in total productivity export. This finding highlights the unusual, prolonged collapse in export production in the Atlantic (which we have confirmed with Ba/Fe measurements). We are left with a puzzle: why did Atlantic productivity take so long to recover?

Figure 2: History of export production in the Atlantic and ecosystem structure in the Pacific across the Cretaceous-Paleogene mass extinction event. From left to right: Atlantic export production (shown by Ba/Fe) collapsed following the extinction and was depressed for the next ~3 million years. In the Pacific, the mass accumulation rate of nannoplankton also fell precipitously while foraminiferal production boomed immediately after the extinction. Fish production (seen in the flux of teeth and bone) seems to have been nearly unchanged by the immediate consequences of the extinction—similar to our results for Pacific export production (not shown). We remain puzzled as to why Atlantic ecosystems fail to rebound like those in the Pacific ocean despite broadly similar biota.

Some Recent Publications

Hull, P.M., and Norris, R.D., 2009. Evidence for abrupt speciation in a classic case of gradual evolution. PNAS 106 (50) 21224-21229.DOI: 10.1073/pnas.0902887106.

Schulte, P. et al., 2010. The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary. Science. 327:1214, DOI: 10.1126/science.1177265.

Carilli, J.E., Godfrey, J., Norris, R.D., Sandin, S. A., Smith, J.E., 2010. Periodic endolithic algal blooms in Montastrea faveolata corals may represent periods of low-level stress. Bulletin of Marine Science 86 (3) 709-718.

Darcy E. Ogden

Assistant Professor of Geophysics


Phone extension:

Research Interests: Application of computational fluid dynamics models to explosive volcanic eruptions. Supersonic volcanic jets. Formation and evolution of volcanic vents. Fluid-Structure Interaction problems in Geosciences.

In explosive volcanic eruptions, rapidly expanding particulate-laden gases decompress through erodible and brittle vents. The shape of the vent can change in response to the stresses applied by the fast-moving expanding gas, which, in turn, is controlled by the vent shape. In particular, 3D vent shape and size has a strong influence on the pressures and velocities of the eruptive fluid, which can have dramatic effects on eruption dynamics. With collaborators at Los Alamos National Laboratory (LANL), I use computational simulations to determine the effect of vent formation on the evolution of an eruption column through time. These projects include both the theoretical aim of more fully understanding the dynamics of supersonic turbulent flow at volcanic scales and the practical goal of quantifying these effects for application to volcanic hazards analysis.

Over the past year, work toward solution of this problem has been composed of two main sub-projects: determining the effects of fixed vent shapes on eruption behavior and development of Fluid-Structure Interaction (FSI) models for geoscience application. I performed a series of numerical simulations of high-speed eruptive fluid expanding through fixed volcanic vents with different geometries. These simulations show that increasing vent curvature or angle results in much wider plumes than those predicted from the 1D analyses frequently used for hazard assessment (Fig.1). These wider plumes have a much greater propensity to collapse and form dangerous pyroclastic density currents (PDCs) that threaten surrounding communities. These results may also suggest a mechanism by which part of an eruption column can collapse and form PDCs, while the rest of the column forms a large buoyant plume. These “transitional columns” are a frequently observed but poorly

understood phenomenon. A change in vent curvature may also cause the formation of strong standing shock waves that radically alter the velocity structure and behavior of volcanic plumes. In reality, the shape of a volcanic vent may change throughout the eruption. Capturing this complex coupled problem requires application and development of sophisticated FSI models that are capable of treating both the fluid dynamics of a high-speed multiphase fluid and the solid mechanics of brittle, erodible rock. With collaborators at Los Alamos National Laboratory (LANL), we have developed a preliminary series of fully coupled numerical simulations of explosive eruptions with evolving volcanic vents (e.g., Fig. 2). These simulations demonstrate the importance of eruption pressure on volcanic vent formation and show a non-uniform distribution of lithic fragments in the eruption column. These results may have important implications for plume evolution throughout an eruption and the interpretation of lithic-rich field deposits.


Ogden, D.E., Wohletz, K.H., Glatzmaier, G.A., & Brodsky, E.E., 2008a. Numerical simulations of volcanic jets: Importance of vent overpressure. J. Geophys. Res., 113, B02204.

Ogden, D.E., Glatzmaier, G.A., Wohletz, K.H., 2008b. Effects of vent overpressure on buoyant eruption columns: Implications for plume stability. Earth Planet. Sci. Lett., 268 (3-4), 283-292.

Robert L. ParkerProfessor of Geophysics, EmeritusEmail: [email protected]: 42475

Research Interests: Inverse theory, geomagnetism, spectral analysis, elec-tromagnetic induction.

The past year has been occupied with bringing to publication workthat was the subject of Ashley Medin’s PhD project. In collaboration withProf Steve Constable in IGPP, and two colleagues in the UCSD Mathe-matics Department, Profs Randy Bank, and Philip Gill, Bob Parker andDr Medin (now Ashley Van Beusekom) have been pursing a radicalapproach to the numerical solution of large-scale inverse problems, apply-ing the ideas to the 2-dimensional magnetotelluric (MT) inverse problem.MT sounding consists in the simultaneous measurement of electric andmagnetic fields on an array of instruments at the Earth’s surface, relyingon naturally generated time-varying fields from the ionosphere and mag-netosphere to provide a driver for electromagnetic induction. As readersof the Annual Report will be aware, electrical methods have risen toprominence as powerful tools for exploring the Earth, particularlybeneath the seafloor. The observational techniques have made enormousstrides in the last decade, with IGPP leading the way. New theoreticalmethods are needed to deal with the volume of data and the demands forhigher resolution.

As a first step in this direction we have adopted a strategy for thesolution of the 2-dimensional MT problem embedded within a numericaloptimization program. In the conventional approach to nonlinear inverseproblems like this one, we begin with a model structure and compute itsresponse and thus predict the observations that would be obtained; this isthe solution of the forward problem. Naturally, at first these predictionsfail to match the actual values, and so the discrepancies are used as abasis for a calculation seeking perturbations to the model that will bringpredictions and observation into better accord—the inverse problem. Theresponse of the modified model is computed and the process repeated. Inthis traditional scheme optimization plays an important part in the sec-ond phase to minimize undesirable features of the new solution (likeexcessive short-wavelength undulations).

The new technique places the whole process under the control of anoptimization algorithm, by including the solution of the forward problemas well as the matching of the observations and the stabilization issuesinto a single objective function, symbolically:

P = w1 ⋅ [PDE violation] + w2 ⋅ [data misfit] + w3 ⋅ [model roughness]

The solution the forward problem entails the numerical solution differen-tial equations derived from Maxwell’s equations, and that process isframed as minimizing an error function; this avoids solving the forwardproblem to needless accuracy and high resolution in the early stages. Torealize these ideas we adopted a general-purpose, multigrid optimizer,PLTMG, created by Prof Bank.

Ω

The plot illustrates the solution based a standard 2-dimensional MT dataset employing both transverse and transverse magnetic responses.Among the advantages of the optimization method developed here is theability to include inequality constraints on the model, in addition to, orinstead of common regularization penalties. Inequalities in inverse prob-lems have been one of Bob Parker’s obsessions: they provide a means forextract reliable information from an inverse problem, somethinglamentably absent in most cases. A paper covering the work describedhere is under review with Geophysical Journal International.

Recent PublicationsParker, R. L., Can a 2-D MT frequency response always be inter-

preted as a 1-D response?, Geophys. J. Internat.,doi: 10.1111/j.1365-246X.2010.04512.x 181, pp 269-74, 2010.

David T. Sandwell Professor of GeophysicsEmail: [email protected] Phone: 47109

Research Interests: Geodynamics, global bathymetry, crustal motion modeling

During the 2010 academic year, Dave Sandwell's research was focused on solid Earth Geophysics with an emphasis on understanding the dynamics of the crust and lithosphere. Our group comprises three graduate students Karen Luttrell, Meng Wei, and Xiaopeng Tong. Our research is mostly supported by three grants; two are from the National Science Foundation with titles Observations and Modeling of Shallow Fault Creep Along the San Andreas Fault Zone and High-Resolution Gravity, Topography, and Seafloor Roughness while the third is from NASA to perform Geodetic Imaging and Modeling of the San Andreas Fault System.

Radar Interferometry - After five years in orbit, the L-Band synthetic aperture radar (SAR) aboard the Japanese ALOS spacecraft is performing beautifully and is providing global interferometric crustal motion measurements. Xiaopeng Tong, David Sandwell and co-investigators, are using these data to investigate the coseismic deformation associated with the 2010 M8.8 Maule, Chile earthquake (Figure 1). We are developing new methods for mosaicking the numerous interferograms covering the 800 km by 300 km zone of deformation. This involves the development of new ScanSAR interferometry methods and code (http://topex.ucsd.edu/gmtsar).

Global Bathymetry - David Sandwell and Walter Smith (NOAA - Silver Spring Maryland) continued their collaboration on retracking the raw radar altimeter waveforms from ERS-1 and Geosat to further improve the accuracy and resolution of the global marine gravity field (Sandwell and Smith, 2009). J.J. Becker has used ship soundings to estimate the slope of the ocean floor in relation to the critical slope needed to convert tidal energy into internal waves (Becker and Sandwell, 2008). This research helps to resolve the issue of, where and how, deep-ocean mixing occurs. The global bathymetry grid is used to search for uncharted seamounts (Sandwell and Wessel, 2010)

Crustal Motion Modeling - Bridget Konter-Smith (now at the University of Texas, El Paso) continued her development of a semi-analytic model for the deformation of western North America that is consistent with the growing array of continuous GPS and InSAR measurements (Smith and Sandwell, 2009). This model was used to predict the crustal stress at seismogenic depth and at various times in the past. Karen Luttrell performed a series of GPS measurements in the Salton Trough area of California in order to measure the viscoelastic rebound of the lithosphere in response to unloading of Lake Cahuilla 300 years ago. Cyclic loading from Lake Cahuilla changes the stress field along the San Andreas Fault and could perhaps trigger a major rupture (Luttrell et al., 2007).

More information is provided at http://topex.ucsd.edu.

Figure 1. Radar interferometry of the 2010 M8.8 Maule, Chile Earthquake. Nine tracks of ALOS ascending interferograms and two tracks of ALOS descending interferograms cover a wide area from the coastline of central Chile to the foothills of the southern Andes.

Relevant Publications Becker, J. J., D. T. Sandwell, (2008) Global estimates of seafloor slope from single-beam ship

soundings, J. Geophys. Res., 113, C05028, doi:10.1029/2006JC003878. Luttrell, K., D. Sandwell, B. Smith-Konter, B. Bills, and Y. Bock, (2007) Modulation of the

earthquake cycle at the southern San Andreas fault by lake loading, J. Geophys. Res., 112,B08411, doi:10.1029/2006JB004752.

Luttrell, K., and D. Sandwell (2010), Ocean loading effects on stress at near shore plate boundary fault systems, J. Geophys. Res., 115, B08411, doi:10.1029/2009JB006541.

Sandwell, D. T., D. Myer, R. Mellors, M. Shimada, B. Brooks, and J. Foster, (2008) Accuracy and resolution of ALOS interferometry: Vector deformation maps of the Father's Day Intrusion at Kilauea, IEEE Trans. Geosciences and Remote Sensing, 46, no. 11, p. 3524-3534.

Sandwell, D. T., and W. H. F. Smith, (2009) Global marine gravity from retracked Geosat and ERS-1 altimetry: Ridge segmentation versus spreading rate, J. Geophys. Res., 114, B01411, doi:10.1029/2008JB006008.

Smith, B., and D. T. Sandwell, (2009) Stress evolution of the San Andreas fault system: Recurrence interval versus locking depth, Geophys. Res. Lett., 36, L13304, doi:10.1029/2009GL037235.

Sandwell, D. T., and P. Wessel, (2010) Seamount discovery tool aids navigation to uncharted seafloor features, Oceanography, 23:1 , p. 24-26.

Tong, X., D. T. Sandwell, and Y. Fialko, (2009) Coseismic Slip Model of the 2008 Wenchuan Earthquake Derived From Joint Inversion of InSAR, GPS and Field Data, J. Geophys. Res., 115, B04314, doi:10.1029/2009JB006625.

Wei, M., D. Sandwell, and Y. Fialko (2009), A silent Mw 4.7 slip event of October 2006 on the Superstition Hills fault, southern California, J. Geophys. Res., 114, B07402, doi:10.1029/2008JB006135.

Annika Sanfilippo

Specialist, RTAD


Phone: 858-534-2049

Research Interests: Radiolarian evolution, taxonomy and stratigraphy, magnetobiostratigraphic chronology and correlation of Cenozoic marine sequences, extinction and diversification associated with climate change during the Paleogene.

A major activity this year has been the continuation of work stimulated by the World Registry of Marine Species (WoRMS) and the Encyclopedia of Life (EOL) to add radiolarian species names, new taxa described in the literature, updating synonyms and make a radiolarian contribution towards a paper on the known versus the unknown global diversity (extant only). During the past year I started to re-examine the gradual evolution in a known Eocene radiolarian lineage using more sophisticated data gathering techniques to collect morphological evidence hypothesizing that morphological variation is distributed continuously across the range of possibilities.

My paleontological research and interest are intimately linked to the geological collections and their proper curation. As the curator for the U.S. West Coast Repository for the DSDP/ODP Micropaleontological References Centers I have inventoried 2000 new radiolarian and diatom slides that have been added to the collection. Work over the past year also includes revitalization and inventory of unique, retired and/or orphaned paleontological collections acquired by SIO Geological Collections as an important contribution to future paleontologists. An orphaned calcareous nannofossil collection has been inventoried and transferred to the Antarctic Marine Geology Research Facility at Florida State University where it will contribute to current research.


Brabb, E.E., Ristau, D., Bukry, D, McDougall, K., Almgren, A.A., Saul, L.-E., and Sanfilippo, A., 2008. Newly discovered Paleocene and Eocene rocks near Fairfield, California, and correlation with rocks in Vaca Valley and the so-called Martinez Formation or Stage. USGS Open Files. Submitted 24 June, 2008. Online: http://pubs.usgs.gov/of/2008/1228

Nigrini, C., Sanfilippo, A., and Moore, T.C., Jr., 2006.Cenozoic radiolarian biostratigraphy: A magnetobiostratigraphic chronology of Cenozoic sequences from ODP Sites 1218, 1219 and 1220, equatorial Pacific. In: Wilson, P.A., Lyle, M., and Firth, J. (eds.), Proc. ODP Sci. Results, 199: College Station, TX (Ocean Drilling Program) 199 http://www-odp.tamu.edu/publications/199_SR/225/225.htm. [Cited YYYY-MM-DD]

Moore, T.C., Jr., Backman, J., Raffi, I., Nigrini, C., Sanfilippo, A., Paelike, H., and Lyle, M., 2004. The Paleogene tropical Pacific: Clues to circulation, productivity and plate motion. Paleoceanography, 19, PA3013, doi10.1029/2003PA000998

Sanfilippo, A., Hakyemez, A., and Tekin, U.K., 2003. Biostratigraphy of late Paleocene-Middle Eocene radiolarians and foraminifera from Cyprus. Micropaleontology, 49(1):47-64.

Sanfilippo, A. and Fourtanier, E., 2003. Oligocene radiolarians and diatoms from the Great Australian Bight (Site 1128, ODP Leg 182). In: Feary, D.A., Hine, A.C., Malone, M.J., et al., (eds.) Proc. ODP, Sci Results, 182: College Station, TX (Ocean Drilling Program). http://www-odp.tamu.edu/publications/182_SR/004/004.htm

Sanfilippo, A. and Blome, C.D., 2001. Biostratigraphic implications of mid-latitude Paleocene-Eocene radiolarian faunas from Hole 1051A, Ocean Drilling Leg 171B, Blake Nose, western North Atlantic. In: Kroon, D., Norris, R.D., and Klaus, A. (eds.), Western North Atlantic Paleogene and Cretaceous Paleoceanography. Geological Society, London, Special Publication 183, pp. 185-224.

John G Sclater

Professor of Marine Geology and Geophysics

Email: [email protected]

Phone: 858-534-3051

Research interests: Tectonic History of the Southwest Indian Ridge with emphasis on the Andrew Bain Mega-transform Fault; Thermal models of old ocean floor; History of science; Heat flow and subsidence of the continental margins of the Gulf of California.

My recent research has concentrated on two major areas: the tectonic history of the Southwest Indian Ridge with an emphasis on the Andrew Bain mega-transform fault and the heat flow through, and the subsidence of, the ocean floor. In addition, I have had a small involvement in the work of Chris and Yuri Fialko on the modeling the slip on oceanic and continental transform faults.

The Southwest Indian Ocean ridge between 15°E and 35°E includes a long continuous section of ridge between 15°E and 25°E and the Andrew Bain Transform Fault complex between 25°E and 35°E that essentially separates the entire Southwest Indian Ridge between the Bouvet Triple junction and the Indian Ocean Triple junction into two distinct morphological systems. Building on earlier studies of the Andrew Bain (Grindlay et al., 1998; Sclater et al., 2005), SIO student Chris Takeuchi (Takeuchi et al., 2010) compared surveys of the actual ridge axis and accretionary zones to the southwest of the Andrew Bain with those to the northwest.

In this last paper (Takeuchi et al., 2010) we report that no single mechanism could produce the observed variable intra-segment lithospheric thickness and melt delivery either side of the Andrew Bain Transform Fault. In the northeast, MBA lows, shallow axial depths, and large abyssal hills indicate that the Marion hot spot enhances the melt supply to the segments. We argued that along axis asthenospheric flow from the hot spot, dammed by major transform faults, produces the inferred asymmetries in lithospheric thickness and melt delivery. In the southwest, strong rift valley curvature and non-volcanic seafloor near the Andrew Bain transform fault indicate very thick sub-axial lithosphere at the end of the single segment. We suggest that cold lithosphere adjacent to the eastern end of the ridge axis cools and thickens the sub-axial lithosphere, suppresses melt production, and focuses melt to the west. This limits the amount of melt emplaced at shallow levels near the transform fault. Our analysis suggests that the Andrew Bain divides a high melt supply region to the northeast from an intermediate to low melt supply region to the southwest. The major results from this work are (1) that this transform fault represents not only a major morphological boundary but also a major melt supply boundary on the Southwest Indian Ridge and (2) that the MBA high and the absence of any magnetic anomalies argued that their was little or not volcanism associated with the emplacement of ocean floor at the boundary of the cold southwest Indian ocean spreading center with the Andrew Bain and that this area probably represents the direct intrusion of mantle rocks onto the ocean floor.

Chris and I returned to the Andrew Bain as part of an Italian/Russian/American expedition on board the R/V Strakhov of the Russian Academy of Sciences. The objectives of this expedition were to dredge the southwestern ridge section and to complete the original survey of the Andrew Bain. Due to a major steering malfunction, we had to abandon the surveys about two thirds of the way into the cruise. Interestingly, mainly basalts and dolerites were dredged from the western axis of the southwestern survey area and harzburgites and lherzolites were recovered from the inside corner uplift. On the wall of the adjacent transform faults mainly basalts and dolerites were found (Peyve et al., 2007). Unfortunately despite three attempts, no samples were recovered from the presumed non-volcanic intrusion zone at the ridge transform intersection.

My second major research effort has been in the area of heat flow and subsidence studies of the ocean floor. In their important paper on the thermal structure of the continental and oceanic lithospheres, McKenzie et al., (2005) stressed that the depth of earthquakes is a widely used parameter that provides first-order indications on the mechanical properties of the lithosphere. They pointed out that earthquakes on old continental lithosphere almost all are confined to crustal regions cooler than 600°C. For the oceans they pointed out that, except for the outer trench, many large intra-plate earthquakes occur at depths where the temperature does not exceed 600°C. In their analysis, McKenzie et al. (2005) show that the temperature dependence of the mantle thermal conductivity results in a deepening isotherms within the oceanic lithosphere. However, of the 68 earthquakes that they examined, 7 still lie significantly below the 600°C isotherm. In a paper that amplified their data form the oceans, Louis Gelli and I showed that two other effects are important. The first is that at young ages any error in age can have a significant effect when comparing the depth of the earthquake with the 600°C isotherm. The second is that many of the earthquakes are on large transform faults or fracture zones and the cooling effect of deep hydrothermal circulation could significantly deepen the 600°C isotherm below these features. Taking into account these two features reduces the number of earthquakes lying below the 600°C isotherm to two and even one of these events has a very unique signature that makes it difficult to interpret. By reducing the number of outliers from seven to two we have substantially increased the validation of the arguments raised by Mckenzie et al. (2005) that mantle temperature is the governing parameter that controls the depth of oceanic earthquakes. In addition, the strong tendency of earthquakes in the Indian Ocean to be located on or near fracture zones suggests that seawater circulation to much more significant depths that was considered previously increases the depth of brittle failure and explains the unexpectedly deep depths of these earthquakes. These results provide indirect evidence that seawater circulates deeply along faults well off axis in older lithosphere, a process that has been documented so far only on or very near the crest of oceanic spreading centers.

Marcel Croon (an SIO student), John Hillier and I (Croon et al. submitted) have submitted a short report to Science Reports criticizing Adam and Vidal (2010) who have reported that sea-floor depth in the Pacific Ocean increases as the square root of distance from the ridge along ‘asthenospheric flow lines’. They argue from this data that this justifies taking a different approach to the topic of lithospheric subsidence that has been the convention in the past. Though their approach is ambitious and provocative, we show that Adam and Vidal (2010) have no real theoretical model to justify their conclusion that they have demonstrated the absence of sea floor flattening in the Pacific. Rather, we show, using data along their flow lines, that the data actually favors a flattening at older ages consistent with at leas two recent analyses of the relation between depth and age for the Pacific Ocean.

Recent Publications

Gelli, L. and J. G. Sclater, 2008. On the depth dependence of oceanic earthquakes: Brief comments on “The thermal structure of oceanic and continental lithosphere”, by McKenzie, D., Jackson, J. and K. Priestly, Earth Plan Sci. Let., 233, 2005, 337-349, Earth Plan Sci. Let., 265, 3-4, 769-775.

Sclater, J. G., N. R. Grindlay, J. A. Madsen and C. Rommevaux-Jestin, 2005. Tectonic interpretation of the Andrew Bain transform fault: Southwest Indian Ocean Geochem, Geophys. Geochem. Geosyst., 6(9) Q09K10, doi:10.1029/2005GC000951.

Crosby, A. G., D. McKenzie and J. G. Sclater, 2006. The relationship between depth, age, gravity in the oceans, Geophys. J. Int., 166, 553-573.

Takeuchi, C. S., J. G. Sclater, N. R. Grindlay, J. A. Madsen, and C. Rommevaux-Jestin, 2010. Segment-scale and intrasegment lithospheric thickness and melt variations near the Andrew Bain megatransform fault and Marion hot spot: Southwest Indian Ridge, 25.5°E–35°E, Geochem. Geophys. Geosyst., 11, Q07012, doi:10.1029/2010GC003054.

Peter Shearer ProfessorEmail address: [email protected] Phone extension: 42260

Research Interests: seismology, Earth structure, earthquake physics

Peter Shearer’s research uses seismology to learn about Earth structure and earthquakes, both globally and in California, and has involved the development of new analysis approaches to handle efficiently the large digital data sets that are now emerging from the global and regional seismic networks. Recent work with former postdoc Catherine Rychert (now at the University of Bristol, U.K.) applies seismic receiver function analysis in a comprehensive study of the lithosphere-asthenosphere boundary (LAB), showing that it is a globally pervasive feature that varies in depth depending upon the tectonic environment (Rychert et al., 2010). Receiver functions provide information only near seismic stations, limiting studies to continents and excluding most of the oceanic crust and lithosphere. SS precursor studies provide more complete global coverage, but traditionally have been used only to image interfaces deeper than the LAB, such as the 410 and 660-km discontinuities, which appear as distinct SS precursor phases. Rychert and Shearer (2010) show that subtle differences in SS waveform stacks can be used to resolve crustal structure, in particular to measure crustal thickness, even in the absence of a separate Moho-reflected phase. They are currently using this approach to map LAB depth and other properties beneath the Pacific and compare their results to those predicted by plate cooling models.

Shearer’s southern California work has focused on improving earthquake locations using robust methods, waveform cross-correlation, and the development of new crustal tomography models to account for 3D velocity variations. Work with former student Guoqing Lin (now at the University of Miami) presents a new unified statewide seismic velocity model for California (Lin et al., 2010), which should help to improve earthquake locations, especially for events situated between the northern and southern California networks. Lin and Shearer (2010) apply a new method to estimate seismic Vp/Vs ratios within 142 similar event clusters across southern California. They obtain a median in situ Vp/Vs ratio of 1.67, which is too low to explain with likely rock types. Instead it suggests the presence of water-filled cracks with several percent porosity in earthquake source regions, which likely has a profound effect on faulting and earthquake activity. In another earthquake location project, visiting scientist Raúl Castro applied the COMPLOC location algorithm of Lin and Shearer (2005) to relocate long-lived aftershocks of the 1887 M 7.5 Sonora, Mexico, earthquake (Castro et al., 2010).

Shearer and Bürgmann (2010) present a review of lessons learned from the 2004 Sumatra-Andaman earthquake, which has been extensively studied because of its great size and devastating consequences. Large amounts of high-quality seismic, geodetic, and geologic data have led to a number of proposed models for its length, duration, fault geometry, rupture velocity, and slip history. The latest of these models vary in their details but now largely agree in their large-scale features, which include significant coseismic slip along the entire 1300- to 1500-km rupture, the bulk of which occurred fast enough to radiate seismic waves (see Fig. 1). The earthquake’s enormous size has challenged conventional processing approaches and stimulated the development of new analysis and inversion methods, including multiple-source inversions, high-frequency body-wave imaging, and satellite observations of tsunami heights and gravity changes. The Sumatra megathrust earthquake was the largest in 40 years and is by far the best documented, but it does not seem fundamentally different in its properties from other large subduction-zone earthquakes. In particular, early reports of anomalously slow slip along its northern segment have not survived more detailed analysis.

Figure 1. Published finite-slip models of the 2004 Sumatra-Andaman earthquake compared with the distribution of the first month of aftershocks and the multiple–centroid moment tensor (CMT) solution of Tsai et al. (2005). The black star shows the location of the earthquake hypocenter, and the gray circle shows the original single CMT location. These plots and the compilation of slip models are courtesy of Martin Mai (http://www.seismo.ethz.ch/srcmod/). From Shearer and Bürgmann (2010).

Recent PublicationsCastro, R., P. M. Shearer, L. Astiz, M. Suter, C. Jacques-Ayala and F. Vernon, The long-lasting aftershock

series of the 3 May 1887 MW 7.5 Sonora earthquake in the Mexican Basin and Range Province, Bull. Seismol. Soc. Am., 100, 1153–1164, doi: 10.1785/0120090180, 2010.

Lin, G., and P. M. Shearer, Evidence for water-filled cracks in earthquake source regions, Geophys. Res. Lett.,36, L17315, doi:10.1029/2009GL039098, 2009.

Lin, G., C. H. Thurber, H. Zhang, E. Hauksson, P. M. Shearer, F. Waldhauser, T. M. Brocher and J. Hardebeck, A California statewide three-dimensional seismic velocity model from both absolute and differential times, Bull. Seismol. Soc. Am., 100, 225-240, doi: 10.1785/0120090028, 2010.

Rychert, C. A. and P. M. Shearer, Resolving crustal thickness using SS waveform stacks, Geophys. J. Int., 180,1128–1137, doi:10.1111/j.1365-246X.2009.04497.x, 2010.

Rychert, C. A., P. M. Shearer and K. M. Fischer, Scattered wave imaging of the lithosphere-asthenosphere boundary, Lithos, doi: 1016/j.lithos.2009.12.006, 2010.

Shearer, P. and R. Bürgmann, Lessons learned from the 2004 Sumatra-Andaman megathrust rupture, Annu. Rev. Earth Planet. Sci., 38, 103–131, doi: 10.1146/annurev-earth-040809-152537, 2010.

Hubert Staudigel

Research Geologist, Lecturer


Personal website: http://earthref.org/whoswho/ER/hstaudigel/index.html


Research Interests: Seamounts, Volcanology, Biogeoscience, Science Cyberinfrastructure and Education

Hubert Staudigel’s research and teaching focuses on seamounts and volcanoes including their petrology, igneous and low temperature geochemistry, hydrothermal processes, microbiology, their magnetic properties, density distribution (gravity) and seismic structure and activity. Recent work includes the geological history and structure of seamounts (Staudigel and Clague, 2010), their role in subduction systems (Staudigel et al., 2010) and deep sea metal deposits (Hein et al., 2010), microbial consortia in their hydrothermal systems (Sudek et al., 2009) and the discovery that fungi in these systems, demonstrating that seafloor alteration is much more similar to soil formation than previously thought (Connell et al., 2009). Staudigel also led the organization of the Seamount Biogeoscience Network (SBN) and the publication of “Mountains in the Sea”, a special volume of Oceanography on seamounts (Staudigel et al., 2010).

Hubert Staudigels’ involvement in volcanology includes interests in submarine volcanism, dike intrusion and collapse and he also teaches a class in volcanology on the Big Island of Hawaii (http://earthref.org/ERESE/courses/HVFT/2010/index.html ). Recent volcanological studies include the paleomagnetic research in Antarctica (Lawrence et al., 2009) and on Jan Mayen, exploring the secular variation of the magnetic field.

Hubert Staudigel collaborates Brad Tebo, Alexis Templeton, Laurie Connell, Katrina Edwards, Craig Moyer and Dave Emerson and graduate students Brad Bailey and Lisa Sudek (Haucke) to study the chemical and biological controls of water-rock interaction during seafloor alteration of the oceanic crust. Current work focuses on the characterization and isolation of microbes that facilitate these processes (Sudek et al, 2009; Bailey et al., 2009), how they colonize rock surfaces and the mechanisms by which microbes may dissolve in particular volcanic glass (Templeton et al, 2010). In a continued collaboration with colleagues at the University of Bergen, (Norway), he contrasted processes of abiotic and biotic tunneling into rock, further exploring how the geological record can be used to study microbial life in volcanoes as far back as 3.5 Ba (McLoughlin et al., 2010). Staudigel continues his ongoing work of microbe-rock interaction in Anarctic extreme environments (http://earthref.org/ERESE/projects/GOLF439/index.html).

Hubert Staudigel and co- principal investigator Cheryl Peach (Stephen Birch Aquarium) collaborate in an NSF-funded GK-12 program, the “Scripps Classroom Connection”, supporting nine Scripps graduate students (per year), in a project that runs until 2014 (http://earthref.org/SCC/). These fellowships offer one year of full-time support to any qualified Scripps PhD student to spend one third of their time in K-12 education while pursuing their thesis work in the remaining time. This project is now in its second year and it involves a close collaboration with nine teachers of the San Diego Unified School District. Fellowships include participation in a four-week summer institute learning about pedagogy and communication, and then they work with their partner teacher for the rest of the year planning and enacting lesson plans in any earth science discipline.

Recent Publications

Bailey B, A. Templeton, H. Staudigel, B. M. Tebo, (2009) Potential utilization of substrate components during basaltic glass colonization by Pseudomonas and Shewanella isolates, Geomicrobiology Journal, Volume 26, 648-656.

Connell, L., A. Templeton, A. Barrett, and H. Staudigel (2009) Diverse fungal consortia associated with an active deep sea volcano: Vailulu’u Seamount, Samoa. Geomicrobiology Journal, Volume 26, 597-605.

Hein, J.R., T.A. Conrad, and H. Staudigel, 2010, Seamount Mineral Deposits: A Source of Rare Metals for High-Technology Industries Oceanography 23-1, 184-189,

Lawrence K. P., L. Tauxe, H. Staudigel, and C. G. Constable, A. Koppers, W. McIntosh, C. L. Johnson (2009) Paleomagnetic field properties at high southern latitude., G-Cubed 10, doi: 10.1029/2008GC002072

McLoughlin, N.,D. Fliegel, H. Furnes, H. Staudigel, A. Simonetti, G.C. Zhao, P.T. Robinson, (2009), Assessing the biogenicity and syngenicity of candidate bioalteration textures in pillow lavas of the ~2.52 Ga Wutai greenstone terrane of China, Chinese Science Bulletin., doi: 10.1007/s11434-009-0448-0.

Sudek, L.A. , Alexis S. Templeton, Bradley M. Tebo and Hubert Staudigel (2009) Microbial Ecology of Fe (hydr)oxide Mats and Basaltic Rock from Vailulu’u Seamount, American Samoa, Geomicrobiology Journal, Volume 26, 581-596

Staudigel H., and D.A. Clague, 2010, The Geological History of Deep-Sea Volcanoes: Biosphere, Hydrosphere, and Lithosphere Interactions., Oceanography 23-1, 58-71.

Staudigel, H., A.A.P. Koppers, J.W. Lavelle, T.J. Pitcher and T.M. Shank (eds. 2010). Mountains in the Sea. Oceanography 23(1): 16-227

Staudigel, H., A.A.P. Koppers, T.A. Plank, and B.B. Hanan, 2010, 176-181.Seamounts in the Subduction Factory Oceanography 23-1, 176-181

Templeton, A. S., E. J. Knowles, D. L. Eldridge, B. W. Arey, A. C. Dohnalkova, S. M. Webb, B. E. Bailey, B. M. Tebo and H. Staudigel, 2009, A seafloor microbial biome hosted within incipient ferromanganese crusts., Nature Geoscience, 2, 872-876.

McLoughlin, N., H. Staudigel, H. Furnes. B. Eickmann and M. Ivarsson (2010) Mechanisms of microtunneling in rock substrates: distinguishing endolithic biosignatures from abiotic microtunnels, Geobiology, 8, 245–255 DOI: 10.1111/j.1472-4669.2010.00243.x

Dave Stegman Research Interests: Global tectonics,Assistant Professor mantle dynamics, planetary geophysics, Email: [email protected] applying high-performance computing Phone: 20767 and 4-D visualization to geodynamics

Dr. Stegman’s research involves computer simulation of plate tectonics using numerical models and high performance computing. The period from 2009-2010 was primarily focused on understanding how the motions of tectonic plates are an expression of the driving forces generated by cooling of the Earth. Recent work has been aimed to further develop a 3-D numerical model of subduction based on a simplified rheology of mature oceanic lithosphere. This approach offers a distinct advantage over traditional mantle convection based studies because the properties of the subducting plate are prescribed a priori and can be controlled exactly for the entire duration of the experiment. The subducting plate has uniform properties for the duration of the experiments, allowing direct comparison with laboratory experiments using analog materials. The numerical models successfully reproduce the entire range of behaviors reported by previous laboratory experiments (shown in Figure 1). Each mode of subduction producesdistinct slab morphologies in the upper mantle resulting from their associated motions of the plate and plate boundary (Stegman et al., 2010b). Additional work reported the influence of far-field boundary conditions on the system (Stegman et al., 2010a) as well as some 2-D

models exploring the interactions with overriding plate (Capitanio et al., 2010). After successfully identifying the parameters that produce the most Earth-like behavior, the work continued to explore how the lateral extent of the plate (i.e. width of the subduction zone) influenced the sinking dynamics and associated plate motions. Another suite of models helped develop a fluid dynamic scaling theory that correctly predicts the behavior of the subducted plate, which is essentially based on the same physics as a penny sinking through a jar of honey. The experiments showed that the velocities of both the plates and the plate boundaries depend on the width of subduction zones and the presence of subduction zone edges. The findings were published in Science (Schellart et al., 2010). The computer models demonstrate that the subducted portion of a tectonic plate pulls on the portion of the plate that remains on the Earth's surface. This pull results in either the motion of the plate, or the motion

of the plate boundary, with the size of the subduction zone determining how much of each. Figure 2 shows a non-linear effect in plate width controls the partitioning for both subducting plates on the Earth as well as the simplified plates in the numerical models. For narrow plates, the subduction is accommodated primarily through slab rollback and trench retreat with very little forward plate motion, but plates with much wider subduction zones subduct

Figure 1: The first suite of numerical models of subduction that exhibit the full range of behavior previously reported by analog laboratory experiments (Stegman et al., 2010b).

almost entirely through plate advance and tend to have more stationary trenches.

Figure 3: Cenozoic evolution of North America illustrating time-evolution of the Farallon plate from an initial width of nearly 11000 km (E) into two narrow plates (G), and corresponding transition from plate advance (E-F) causing compression in the North American continent to trench retreat (G-H) and extension in the Basin and Range province.

Publications for 2009-2010Capitanio, F.A., D. R. Stegman, L. Moresi and W. Sharples. “Upper plate controls on deep subduction, trench migrations and deformations at convergent margins”, Tectonophysics,doi:10.1016/j.tecto.2009.08.020, 483, 80-92, 2010. Farrington, R., D. R. Stegman, L. Moresi, M. Sandiford and D.A. May. “Interactions of 3D Mantle Flow and Continental Lithosphere near Passive Margins,” Tectonophysics, 483, 20-28, 2010. Stegman, D.R., W.P. Schellart, and J. Freeman. “Competing influences of plate width and far-field boundary conditions on trench migration and morphology of subducted slabs in the upper mantle,” Tectonophysics, doi:10.1016/j.tecto.2009.08.026, 483, 46-57, 2010a. Stegman, D.R., R. Farrington, F.A. Capitanio, and W.P. Schellart. “A regime diagram for subduction styles from 3-D numerical models of free subduction,” Tectonophysics,doi:10.1016/j.tecto.2009.08.041, 483, 29-45, 2010b. Yanagisawa, T., Y. Yamagishi, Y. Hamamo, and D. R. Stegman. “Mechanism for generating stagnant slabs in 3-D spherical mantle convection models at Earth-like conditions”, Physics of the Earth and Planetary Interiors, 2010 (in press). Schellart, W.P., D. R. Stegman, R.J. Farrington, J. Freeman, and L. Moresi. "Cenozoic Tectonics of Western North America Controlled by Evolving Width of Farallon Slab", Science, 329, 5989, 316-319, doi: 10.1126/science.1190366, 2010.

Figure 2: Partitioning of plate motions shown as the fraction of the subduction rate (Vs) that is accommodated by forward plate motion (Vsp) for 16 natural subduction zones on Earth (left) and 11 numerical models (right). The curve uses the fluid dynamic scaling based on the sinking dynamics of an oblate ellipsoid. Narrow plates preferentially subduct through motion of the plate boundary rather than motion of the subducting plate.

Lisa Tauxe

Distinguished Professor of Geophysics

Email address: [email protected], website: http://magician.ucsd.edu/~ltauxe/

Phone extension: x46084

Research Interests: Behavior of the ancient geomagnetic field. Statistical analysis of paleomagnetic data. Applications of paleomagnetic data to geological problems.

My research over the past year has focused on a few major themes including: 1) variations in the strength of the geomagnetic field over the past seven millennia as recorded in Israeli and Jordanian copper mining slag heaps, and 2) paleomagnetic and rock magnetic studies of sediments recovered during IODP Expedition 318 on the Wilkes Land margin and the Adelie Basin, Antarctica.

Topic #1: Last year we reported on data obtained from an excavation led by Prof. T.E. Levy (Dept. of Antrhopology, UCSD) of a thick pile of copper mining slag in Jordan. Our results, published by Ben-Yosef et al. (2009) demonstrated rapid changes in field intensity in a period of overall high field values. This year, we excavated a second section in a nearby Israeli site thought to be the same age (Figure 1). Our results from this second excavation replicated the first and documented two episodes of extremely high magnetic fields and extremely rapid rate of change (Shaar et al., submitted). Furthermore, Shaar et al. (2010) published results examining the behavior of copper mining slag and established its reliability for archaeointensity research. Finally, in a pair of papers, Ben-Yosef et al. (2010a,b) extended our research to older material.

Figure 1: Excavation in Timna Valley, Israel. To the right is a small slag mound which is co-eval with the mound described by Ben-Yosef et al. (2009).

Topic #2: The Antarctic cryosphere plays a key role in the global climate system and its history therefore plays a role in the current climate change debate. Drilling on the Antarctic Wilkes Land margin (IODP Expedition 318, January – March, 2010) was designed to recover sedimentary

archives documenting the onset of glaciation at ~34 Ma and its entire history up to and including the Holocene. A critical aspect of the goals of the expedition is documenting the age of the sediments and sedimentary hiatuses. Extensive paleomagnetic analyses were carried out during the expedition. The magnetic stratigraphy provides crucial constraints on the position and duration of hiatuses as well as calibration for the biostratigraphies in the southern ocean, where direct calibration is notably scarce. Furthermore, magnetic fabrics, mineralogy and grain size provide intriguing clues to environmental changes recorded in this unique sedimentary sequence.

Figure 2: Location of IODP Expedition 318 drill sites on the Wilkes Land Margin.


Ben-Yosef, E., Tauxe, L., Levy, T.E., Shaar, R., Ron, H., and Najjar, M., Archaeomagnetic intensity spike recorded in high resolution slag deposit from historical biblical archaeology site in Southern Jordan, Earth Planet. Sci. Lett., doi:10.1016/j.epsl.2009.09.001, 2009

Ben-Yosef, E., Levy, T.E., Smith, N.G., Higham, T., Najjar, M. and Tauxe, L., The beginning of Iron Age copper production in the southern Levant: new evidence from Khirbat al-Jariya, Faynan, Jordan, Antiquity, 84, 724-746, 2010a.

Ben-Yosef, E., Tauxe, L., Levy, T.E., Archaeomagnetic dating of copper smelting site F2 in the Timna Valley (Israel) and its implications for the modelling of ancient technological developments, Archaeometry, doi: 10.1111/j.1475-4754.2010.00528, 2010b.

Shaar, R., Ron, H., Tauxe, L., Kessel, R., Agnon, A., E. Ben-Yosef, J.M. Feinberg, Testing the accuracy of absolute intensity estimates of the ancient geomagnetic field using copper slag material, Earth Planet. Sci. Lett., 290,201-213, 2010.

Michael Tryon

Project Scientist


Phone extension: 20591 Web page: http://TryonLab.ucsd.edu

Research Interests: The marine hydrogeology of cold seeps, mud volcanoes, and submerged faults, the physical and chemical processes associated with the structural evolution of convergent margins, and the development of new seafloor instrumentation for investigations of the above processes.

My research over the past year has been divided between two field projects (West Nile Delta, Muddy Waters), two instrument development projects (GEOCE, PUPPI-II), and analysis/synthesis and manuscript preparation for earlier field projects in Alaska, Costa Rica, and the Sea of Marmara.

Mud volcanism is a common phenomenon in accretionary margins and deltaic depositional systems worldwide. Fluid formation and fluidization processes occurring at depths of several kilometers below the seafloor can be monitored in mud volcanoes acting as natural windows to processes unreachable by other means. To gain a better understanding of deep processes occurring in such environments, I have two ongoing projects. In the West Nile Delta area, I am carrying out a study on two mud volcanoes in collaboration with researchers at IFM-GEOMAR. This project focuses on qualifying the chemical and isotopic composition of pore fluids as well as investigations of light volatile hydrocarbon gases and organic biomarkers and the quantification of the variability of dewatering and degassing through long-term flow rate and chemical flux measurements. The Muddy Waters project, in collaboration with researchers at MARUM, Bremen, investigates mud volcanoes and thrust faults south of Crete to gain insight on the so-called intermediate loop of the subduction factory; the region arcward of the frontal prism but seaward of the arc volcanism.

I have two instrument development projects ongoing. The first of these is the development of an ocean bottom 3-D strain meter, GEOCE, in collaboration with D. Chadwell and U. Send, both at Scripps. My portion of this project uses high resolution pressure measurements and a seafloor pressure standard to determine the vertical motion of the seafloor in response to tectonic deformation and/or gravitational sliding. The data from the shallow engineering deployment off Torrey Pines indicates we are near to achieving the goal of 1 cm resolution in 3 dimensions. A final deep test deployment is currently ongoing near Catalina Island. My second instrumentation project is the development of a new generation of seafloor piezometers for both long-term monitoring of the hydrological response to tectonic strain and for geotechnical investigations (PUPPI-II). Construction is nearly completed and sea trials are about to begin. These two instrumentation development programs will allow us to monitor the most critical properties (stress and strain) of continental margins to improve our understanding of the underlying tectonics and for evaluation of their potential for catastrophic failure.

The MARNAUT Project is an international collaboration utilizing a wide array of geophysical and hydrological techniques to study the manifestations of fluid expulsion associated with the Main Marmara Fault, the submerged western extension of the North Anatolian Fault Zone in Turkey, with the theme of understanding the relationship between seismic activity and fluid migration/expulsion processes along this active plate boundary. Our results confirm a direct relationship between seafloor faults and water and gas emissions with active expulsion tied to earthquake activity and seismic gaps associated with a lack of expulsion (Géli et al., 2008). The main strike-slip fault intersects fluid sources many kilometers below the seafloor and provides a pathway for oil and thermogenic gas as well as

formation fluids with high salinities and exotic chemistry indicative of a very deep source, potentially within the seismogenic zone. Extensional tears in the NW Tekirdag Basin expel plumes of CO2 rich in mantle 3He. Basin boundary extensional faults intersect near-surface sources of methane and buried Pleistocene Lake Marmara water (Tryon et al., 2010a).

The margins community has only relatively recently begun to examine the substantially different tectonics and associated hydrologic systems of erosive convergent margins as compared with accretionary margins. One type example is the Costa Rica system which has been the subject of numerous recent large-scale investigations as well as our 2005-2007 investigations at mid-slope mud volcanoes Mound 11 and 12 and at Jaco Scar. Pore fluids expelled at the wedge toe and at these mud volcanoes have been previously interpreted to have the same deep source of dehydrating clays however our investigations indicate they have boron and lithium concentrations and ratios that are incompatible with this explanation. Our analyses suggest that the fluid chemistry, and particularly the extremely high B/Li molar ratios, seen at a recent mud flow on Mound 11 is the result of a fluid source rich in eroded material from the serpentinized upper plate that has been subducted to higher temperatures and released excess B into the pore fluids (Tryon et. al, 2010b, Füri et al, 2010).

Recent Publications

Tryon, M.D., P. Henry, M.N. Çagatay, T. Zitter, L. Géli, L. Gasperini, P. Burnard, S. Bourlange, and C. Grall, Pore fluid chemistry of the North Anatolian Fault Zone in the Sea of Marmara: A diversity of sources and processes, Geology, Geophysics, and Geosystems (G-Cubed),doi:10.1029/2010GC003177, 2010a.

Tryon, M.D., Wheat, C.G., Hilton, D.R., Fluid sources and pathways of the Costa Rica erosional convergent margin, Geology, Geophysics, and Geosystems (G-Cubed), doi:10.1029/2009GC002818, 2010b.

Füri, E., D.R. Hilton, M.D. Tryon, K.M. Brown, G.M. McMurtry, W. Brückmann, and C.G. Wheat, Carbon release from submarine seeps at the Costa Rica fore-arc: Implications for the volatile cycle at the Central America convergent margin, Geology, Geophysics, and Geosystems (G-Cubed),10.1029/2009GC002810, 2010.

Tryon, M.D., Monitoring aseismic tectonic processes via hydrologic responses: An analysis of log-periodic fluid flow events at the Costa Rica outer rise, Geology, 37 (2), 163-166, 2009a.

Füri, E., D.R. Hilton, K.M. Brown, and M.D. Tryon, Helium systematics of cold seep fluids at Monterey Bay, California (USA): temporal variations and mantle contributions, Geology, Geophysics, and Geosystems (G-Cubed), doi:10.1029/2009GC002557, 2009.

Rathburn, A. E., L. A. Levin, M. Tryon, J. M. Gieskes, J. B. Martin, M. E. Pérez F. J. Fodrie, C. Neira, G.J. Fryer, G. Mendoza, P. A. McMillan, J. Kluesner, J. Adamic, W. Ziebis, Geological and biological heterogeneity of the Aleutian margin (2000-4800 m), Progress in Oceanography, 80, 22-50, 2009.

Barry, P.H., D.R. Hilton, M.D. Tryon, K.M. Brown, J.T. Kulongoski, A New Syringe Pump Apparatus for the Retrieval and Temporal Analysis of Helium (SPARTAH) in groundwaters and geothermal fluids, Geology, Geophysics, and Geosystems (G-Cubed), (Technical Briefs),doi:10.1029/2009GC002422, 2009.

Géli, L., P. Henry, T Zitter, S. Dupré, M. Tryon, M.N. Çagatay, B. Mercier de Lépinay, X. Le Pichon, AMC Sengor, N. Görür, B. Natalyn, G. Uçarkus, S. Özeren, D. Volker, L. Gasperini, P. Bernard, S. Bourlange, and the Marnaut Scientific Party, Gas emissions and active tectonics within the submerged section of the North Anatolian Fault zone in the Sea of Marmara, Earth and Planetary Science Letters,274 (1-2), 34-39, 2008.

Kris Walker Project Scientist Email address: [email protected] extension: 4-0126

Research Interests: infrasound, seismology, array processing methods

Kris Walker has focused on several atmospheric infrasound projects during 2009-10. Most of these projects have led (or are leading) to scientifically interesting results. The other projects are geared toward building infrastructure that will benefit future research.

Infrasonic Source Imaging with the USArray: In collaboration with Michael Hedlin, Catherine de Groot-Hedlin, and other researchers at the Naval Research Lab and Commissariat à l'Energie Atomique, Kris compared the performances of the USArray and four globally spaced infrasound arrays to analyze a meteor explosion that occurred in northeast Oregon in 2008 (Walker et al., in press). He used reverse-time migration to back-project USArray vertical broadband recordings of acoustic-to-seismic coupled signals that were observed out to a range of 800 km. The source imaging suggests that these signals are explained by a terminal burst rather than a line source associated with a hypersonic trajectory through the atmosphere. Using the bootstrap method, he determined the 95% confidence region of the source location in 3-D space and time (Fig. 1). The source altitude, video camera constraints, and variance in final source locations provided by different algorithms suggest that the hypersonic trajectory had a minimum speed of 40 km/s. The spatial source location uncertainty was an order of magnitude smaller than that typically provided by globally spaced infrasound arrays, suggesting that despite the complexities associated with station-to-station variations in subsurface geology, it is more useful, for location purposes of energetic events, to analyze seismic recordings from dense seismometer networks than to analyze infrasound recordings from infrasound arrays with an average inter-array spacing of 2300 km.

Fig. 1. Comparison of source locations and 95% confidence regions for the bolide burst source location estimated with the USArrayseismic network (Final RTM) and infrasound arrays in North America. The infrasound array source locations are derived with differenttechniques and assumptions depending on if only back azimuths were used (A), if both back azimuths and times were used (AT), and if a wind correction is performed (WC or NWC). PNSN is the Pacific Northwest Seismic Network source location.

Kris is also using reverse-time migration (RTM) with the USArray to systematically locate infrasonic sources with undergraduate Richard Shelby and Michael Hedlin. Hundreds of sources have been detected thus far using this technique in 2008. For example, Fig. 2 is a USArray “infrasonic image” of a Vandenberg Air Force Base rocket launch. This figure shows the analyst’s picking tool used to identify events of interest by manually inspecting peaks in an automatically calculated detector function, which is

based on the RTM data. There is on average one U.S. event observed per day. More interesting are the propagation and source patterns observed in the data. Kris submitted an NSF proposal to extend this study to span 2004-2009. The development of a catalog of events detected with the USArray has a broader impact in infrasound research because there are generally few publically available ground truth catalogs of infrasonic events, which can be used to test a variety of infrasound propagation hypotheses as well as validate new 4-D velocity models.

Fig. 2. The Q detector function (upper left) images the source in time; there is a peak at the launch time (thick red line) with a signal-to-noise ratio of 22 dB. Other colored lines indicate known regional and teleseismic earthquake times. The map shows the seismic energy migrated back to the source, where it constructively interferes, imaging the source in space at the source time. The record section to the right shows that the energy associated with the peak moves out at ~300 m/s, indicating that rocket infrasound is observed via acoustic-to-seismic coupling on USArray seismometers (white triangles in map) out to ~1500 km. Horizontally aligned signals are earthquakes.

Optical Fiber Infrasound Sensor (OFIS): The second project Kris is working on is the development of a ruggedized, DC-powered OFIS for remote, autonomous deployments. The OFIS has proven to be more effective than pipe rosettes in mitigating the negative effects of wind in the measurement of infrasound (Walker and Hedlin, 2010). But until recently, this technology has been “fragile” and not been suitable for remote, autonomous deployments. This new development effort is an SIO collaboration with David Chavez, Michael Davis, Ph.D. graduate student Scott DeWolf, David Howitt, Mike Kirk, undergraduate Richard Shelby, Joel White, Frank Wyatt, and Mark Zumberge. In 2008, the OFIS system was an A/C powered research project with a large footprint comprising swappable rack modules, a bench-top laser, an optical polarization manipulation device, a digital signal processor, and a computer attached to an internet switch. The 2008 system also had an interferometer uptime issue associated with temperature change. Fabricated and tested in September 2010, OFIS v. 2.0 is a DC-powered system comprising miniaturized electronic boards, a lower-noise OEM laser with advanced feedback circuit, a low-power computer and digitizer, and a 900 MHz radio that transfers data to an internet switch. Scott DeWolf and Mark Zumberge addressed the uptime issue by adding Faraday mirrors to the sensing and reference optical paths, which eliminate the cumulative effects of temperature-dependent anisotropy. The new system will be deployed in northern California for one year as part of a NOAA-funded research project to study Pacific microbaroms. The new system is now

capable of being deployed around volcanoes or in other remote environments where it is necessary to acquire high-quality, broadband recordings of infrasound in the presence of wind.

El Mayor Mw 7.2 Earthquake: Kris is also collaborating with Catherine de Groot-Hedlin on a study of the infrasound generated by the Baja California Mw 7.2 earthquake (Walker and de Groot-Hedlin, 2010). Two infrasound arrays in southern California (MRIAR and I57) recorded a long infrasound wavetrain from this earthquake. Array processing of MRIAR data identifies a clear back azimuth rotation with time that spans the entire ~100 km long rupture. Ray tracing using 4-D velocity models suggests that the wavetrains are refracted thermospheric arrivals, which are inherently interesting because their existences are not predicted based on the classic thermospheric attenuation model. The ray tracing also shows that the MRIAR rotation of back azimuth with time is due to the fact that the northern end of the bilateral rupture is much closer to MRIAR than the southern end. Experiments suggest that we can image the rupture with the MRIAR data in a similar manner to earthquake rupture imaging (e.g. Walker and Shearer, 2009). More information is available at http://hpwren.ucsd.edu/news/20100413/.

Southern California Infrasound Network: Southern California has an impressive seismic network. . Kris is working on the creation of an analogous infrasound array network, which will permit a number of studies in regional sources, propagation, signal processing methods, and wind noise reduction. This collaboration with Mark Zumberge and Michael Hedlin culminated in June 2010 with the deployment of SMIAR, the third southern California infrasound array. More information about SMIAR is available at http://hpwren.ucsd.edu/news/20100701/.

Infrastructure Building for Global and Regional Infrasonic Studies: Infrasonics can be though of as surface-wave seismology turned upside down. There is a renewed interest in infrasonics because of the recent creation of the IMS global infrasound array network and the advent of 4-D global atmospheric velocity models. There are now many opportunities to make contributions to our understanding of infrasound sources, propagation, sensor development, and inversion methods. To facilitate future infrasonics research, Kris is also creating a database of global infrasound array network data and 4-D atmospheric velocity models with which to model infrasonic propagation. Roughly 60% of the global array data and 80% of the 4-D velocity models from 2004 to present are archived at IGPP. Some of these data are considered restricted, but may be published with permission from federal government entities, which is done routinely. Kris seeks undergraduate or graduate students interested in atmospheric acoustics to begin or assist with new research projects.

References:Walker, K.T. and Shearer, P.M., 2009, Illuminating the near-sonic rupture velocities of the intracontinental Kokoxili Mw 7.8 and Denali fault Mw 7.9 strike-slip earthquakes with global P wave back projection imaging, JGR, v. 114, doi:10.1029/2008JB005738.

Walker, K.T., and Hedlin, M.A.H., 2010, A review of wind noise reduction methodologies, in "Global Continuous Infrasound Monitoring for Atmospheric Studies", eds. A. Le Pichon, E. Blanc, and A. Hauchecorne, Springer Geosciences, p. 141-182.

Walker, K.T. and de Groot-Hedlin, C., 2010, Infrasonic observations of ground shaking along the 2010 Mw 7.2 El Mayor rupture: a new tool for creating ground shaking intensity maps?, SCEC Meeting [abstract].

Walker, K., Hedlin, M., de Groot-Hedlin, C., Vergoz, A., Le Pichon, A., Drob, D., Source location of the 19 February 2008 Oregon bolide using seismic networks and infrasound arrays, JGR, [in press].

Brad Werner [email protected] ||| http://complex-systems.ucsd.edu

Research interests: complexity, nonlinear dynamics and pattern formation; permafrost terrain;dynamics of human systems and human-landscape interactions; urban landscapes; dynamics ofwestern and indigenous science; resistance movements; and independent media.

Brad Werner and co-workers Marcel Madison, Weini Mehari, Alice Nash, Christina Rios, ChrisShughrue, Gabriel Velin and Ben Volta (Anthropology/IGPP) in the Complex Systems Laboratoryand collaborator D. Emily Hicks (Chican@ Studies/SDSU) been working to develop and refine thetools used to investigate complex systems, particularly those tools that are necessary to makeuseful predictions for the coupled human/Earth surface system. We also aim to democratizeknowledge of nonlinear dynamics, so that a broader range of people can participate in analyzingand shaping the future of Earth’s surface and the role of humans within its systems.

Dynamics of Urban Landscapes: Slums are the fastest growing segments of cities, and they areoften located in marginal zones most at risk for disasters. The growth of slums and their nonlinearinteraction with economic and landscape systems will play a critical role in Earth surface dynamicsas human population reaches a projected maximum later this century. Weini, Christina, Marcel,Chris and Gabriel have developed a model for the slum Kibera in Nairobi, Kenya, including modulesthat simulate flooding, disease transmission, housing/development, employment, water, food andfuel use, sanitation and waste, crime, migration to and from slums, government and NGOs, andresistance. The individual modules have been completed and their integration is in progress. Ofparticular interest is how the nature of coupled slum-landscape dynamics might change asmigration and slum populations increase, and regional and global economies become stressed.

Ben is modeling Oxpemul and Chichén Itzá, in Yucatan,Mexico, which were thriving Maya cities starting around700-800, underwent significant changes, and latercollapsed. The sites are located in a karstic landscapehighly dependent on episodic rains for water supply andagriculture. Ben’s agent-based model includeshydrology and water storage and use; vegetation andsoil degradation from farming; urban dwellingconstruction and cooperative agriculture based onlineage and social group formation, immigration andemigration, and cultural evolution (An Agent-BasedModel for Self-Organization in Growth of Maya UrbanCenters, Journal of Archeological Science, inpreparation). The model currently lacks organizedpolitical action, external trade and social hierarchy (to beadded later) in an attempt to test the extent to whichvillage-type dynamics can reproduce the temporaldevelopment and spatial layout of the cities. Nonlinearspatial forecasting and other techniques are being usedto compare the model with available data and tocompare the layout of different cities.

Border Complexity: Acting as filtration systems atintermediate time scales to goods and people, nation-state borders interact nonlinearly with distant land use and resource extraction patterns. To clarifythe dynamics of borders, Emily and Brad developed a theoretical description of the Mexico-USborder as a hierarchical complex system (The Mexico-US Border as a Complex System, Theory,Culture and Society, in preparation). Past descriptions of borders were reinterpreted usingcomplexity. For example, the apparent conflict between Bhabha’s view that hybrid border culture is

Modeled location of residences (orange) andagricultural fields (red) on elevation map (darkto light blue) of ancient Maya city of Oxpemul, insouthern Campeche, Mexico. The settlement isdistributed on the elevated areas at the centerof the grid, whereas the fields are located in themore fertile seasonally inundated low-lyingareas surrounding the settlement.

subversive and Kraidy’s argument that hybridity follows the contours of existing power relations canbe resolved by interpreting Bhabha’s argument as applying to a short time scale level of descriptionand Kraidy’s to a longer time scale, where the dynamics of co-optation of subversive behaviors hashad time to play out. Similarly, criticism of Hardt and Negri’s argument that nation-states arebecoming increasingly irrelevant and globally acting systems of economic, political and socialpower are united into a single overarching phenomenon they call Empire - based on the continuingconsiderable power exerted by nation states, especially the US - can be resolved by recognizingthat the dynamics of Empire acts on longer time scales than the dynamics of nation states. Inaddition, the tools of complexity were employed to analyze a series of problems regarding theborder, including the femicides of Cuidad Juarez and the dynamics of the painful experience of anundocumented individual leaving her village, traveling across the border, and becoming establishedin a community in the US.

Resistance, Economic/Political Dynamics, and Landscapes: Given the considerable influence ofhumans on landscapes and of natural processes on humans, and widespread resistance toresource extraction, coupling between the political and economic dynamics determining land use,landscape processes and resistance will be central to determining the future evolution of Earth’ssurface. We are investigating the hypothesis that the emergent capitalist/democracy cultural systemis a relatively formless resource exploiting and consuming machine whose direction and focus areprincipally determined by its interaction with resistance. Chris is developing an agent-based modelfor the dynamics of the occurrence of oil spills by coupling oil industry exploration, production andtechnology development, oil spill response and environmental damage, government regulation,media coverage, environmental advocacy groups and public perception.Response to UCSD’s Racism Crisis and Democratizing Dynamics: Following the most recentmanifestation of UCSD’s racism crisis, the series of racist provocations in February, 2010, membersof the CSL supported student-led responses by attending and documenting protests and providingassistance and advice to individual students through the crisis. In March-May, a series of reflectiveinterviews were conducted with participants that are being combined with live footage into adocumentary. To foster better relations between UCSD and working class communities, acommunity service component was added to undergraduate courses, working with organizations orschools in City Heights and Chula Vista, and a new graduate course, Community Based Science,was developed. In contrast to common ways in which universities interact with working classcommunities of color - mining their most skilled youth as recruits and giving nothing in return orusing interactions with communities for marketing purposes - this course is aimed at teachingstudents to develop genuine, two-way interactions with communities by learning about andparticipating in the community’s struggles, exchanging knowledge and skills, and engaging inprojects that are jointly determined and relevant to the community. These efforts are part of abroader project to help make UCSD more welcoming and to support community struggles in theborder region, including founding Grassroots Diversity Action Working Group in spring 2007 andremaining an active member through February 2010, and participating in immigrant rights andindigenous struggles using media technology. Members of the CSL are working to broaden accessto the tools of complexity by: participating in community workshops and meetings; organizingcomplexity-related discussion groups; sharing technical and knowledge skills and equipment withcommunity activists; meeting with on-the-ground resource managers; developing a park exhibit;and writing popular books on urban complexity and the dynamics of resistance.--B. T. Werner & D.E. McNamara (2007) Dynamics of coupled human-landscape systems, Geomorphology, 91, 393-407.--D.E. McNamara & B. T. Werner (2008) Coupled Barrier Island-Resort Model: 1. Emergent instabilities induced by stronghuman-landscape interactions, JGR-Earth Surface, 113, F01016, doi:10.1029/2007JF000840.--D.E. McNamara & B. T. Werner (2008) Coupled Barrier Island-Resort Model: 2. Tests and Predictions along Ocean Cityand Assateague Island National Seashore, Maryland, JGR-Earth Surface, 113, F01017, doi:10.1029/2007JF00084.--L.J. Plug & B.T. Werner (2007) Modelling of ice-wedge networks, Permafrost & Periglacial Processes, 19, 63-69.

Peter F. Worcester Research Oceanographer and Senior Lecturer Email: [email protected] Phone: 44688

Research Interests: acoustical oceanography, ocean acoustic tomography, underwater acoustics

Peter Worcester’s research is focused on the application of acoustic remote sensing techniques to the study of ocean temperature structure and circulation and on improving our understanding of the propagation of sound in the ocean, including the effects of scattering from small-scale oceanographic variability.

Acoustic Thermometry. Over the decade 1996–2006, acoustic sources located off central California (1996–1999) and north of Kauai (1996–1999, 2002–2006) transmitted to receivers distributed throughout the northeast and north central Pacific [Dushaw et al., 2009]. The acoustic travel times are inherently spatially integrating, which suppresses mesoscale variability and provides a precise measure of ray-averaged temperature. Daily-average travel times at four-day intervals provide excellent temporal resolution of the large-scale thermal field. The interannual, seasonal, and shorter period variability is large, with substantial changes sometimes occurring in only a few weeks. Linear trends estimated over the decade are small compared to the interannual variability and inconsistent from path to path, with some acoustic paths warming slightly and others cooling slightly. The measured travel times are compared with travel times derived from four independent estimates of the North Pacific: (i) climatology, as represented by the World Ocean Atlas 2005 (WOA05), (ii) objective analysis of the upper ocean temperature field derived from satellite altimetry and in situ profiles, (iii) an analysis provided by the Estimating the Circulation and Climate of the Ocean project as

implemented at the Jet Propulsion Laboratory (JPL-ECCO), and (iv) simulation results from a high-resolution configuration of the Parallel Ocean Program (POP) model. The acoustic data show that WOA05 is a better estimate of the time-mean hydrography than either the JPL-ECCO or the POP estimates, both of which proved incapable of reproducing the observed acoustic arrival patterns. The comparisons of time series provide a stringent test of the large-scale temperature variability in the models. The differences are sometimes substantial, indicating that acoustic thermometry data can provide significant additional constraints for numerical ocean models.

Figure 1. Comparison of measured travel times for transmissions from Kauai to receiver k, approximately 4000 km northwest of Kauai, (blue) with travel times calculated using sound-speed fields derived from WOA05, estimates of upper ocean temperature profiles produced by an objective analysis (OA) procedure that combines satellite altimetric height with in situ temperature profiles, the JPL-ECCO solutions, and the POP model (gray). The time means have been removed from all of the time series. For comparison, the trend in travel time corresponding to a 5 m°C/year increase in temperature at the sound-channel axis is also shown (red).

North Pacific Acoustic Laboratory (NPAL). Over the last twenty years, long-range, deep-water acoustic experiments have been performed almost entirely in the relatively benign northeast and north central Pacific Ocean [e.g., Van Uffelen et al., 2009, 2010; Stephen et al., 2010]. The NPAL Group is now conducting acoustic propagation experiments in the much more energetic and variable northern Philippine Sea. A short-term Pilot Study/Engineering Test was conducted in April-May 2009. The one-year-long 2010–2011 NPAL Philippine Sea Experiment, consisting of six acoustic transceivers

and a new Distributed Vertical Line Array (DVLA) receiver, was deployed during April 2010. The 2010–2011 experiment combines measurements of acoustic propagation and ambient noise with the use of an ocean acoustic tomography array to help characterize this highly dynamic region. The tomographic measurements, when combined with satellite and other in situ measurements and with ocean models, will provide an eddy-resolving, 4-D sound-speed field for use in making acoustic predictions.

Figure 2. Overall mooring geometry of the 2010–2011 Philippine Sea Experiment, consisting of six 250-Hz acoustic transceivers (T1, T2, … T6) and a new DVLA receiver. The array radius is approximately 330 km.

The goals are to (i) understand the impacts of fronts, eddies, and internal tides on acoustic propagation in this complex region, (ii) determine whether acoustic methods, together with satellite, glider and other measurements and coupled with ocean modeling, can yield estimates of the time-evolving ocean state useful for making improved acoustic predictions and for understanding the local ocean dynamics, (iii) improve our understanding of the basic physics of scattering by small-scale oceanographic variability due to internal waves and density-compensated small-scale variability (spice), and (iv) characterize the ambient noise field, particularly its variation over the year and its depth dependence. The ultimate goal is to determine the fundamental limits to signal processing in deep water imposed by ocean processes, enabling advanced signal processing techniques to capitalize on the three-dimensional character of the sound and noise fields.


Dushaw, B. D., P. F. Worcester, W. H. Munk, R. C. Spindel, J. A. Mercer, B. M. Howe, K. Metzger, Jr., T. G. Birdsall, R. K. Andrew, M. A. Dzieciuch, B. D. Cornuelle, and D. Menemenlis, 2009: A decade of acoustic thermometry in the North Pacific Ocean. Journal of Geophysical Research, 114, C07021.

Stephen, R. A., S. T. Bolmer, M. A. Dzieciuch, P. F. Worcester, R. K. Andrew, L. J. Buck, J. A. Mercer, J. A. Colosi, and B. M. Howe, 2009: Deep seafloor arrivals: An unexplained set of arrivals in long-range ocean acoustic propagation. Journal of the Acoustical Society of America, 126, 599-606.

Van Uffelen, L. J., P. F. Worcester, M. A. Dzieciuch, and D. L. Rudnick, 2009: The vertical structure of shadow-zone arrivals at long range in the ocean. Journal of the Acoustical Society of America, 125,3569-3588.

Van Uffelen, L. J., P. F. Worcester, M. A. Dzieciuch, D. L. Rudnick, and J. A. Colosi, 2010: Effects of upper ocean sound-speed structure on deep acoustic shadow-zone arrivals at 500- and 1000-km range. Journal of the Acoustical Society of America, 127, 2169-2181.

Mark A. Zumberge




Research Interests: Measurement of gravity and pressure in the marine and subaerial environments, development of new seismic instrumentation, optical fiber measurements of strain and pressure

Monitoring the world’s largest CO2 sequestration reservoir with gravity (In collaboration with Glenn Sasagawa)

A mainstay of our group’s research is the measurement of Earth’s gravity on the seafloor. Gravity, being sensitive to the density of the underlying rock, changes from place to place depending on the geologic structure nearby. We can use it to help create an image of the layered Earth below the survey area. We have carried out gravity surveys to study the structure of mid-ocean ridges and to help reveal the densities of ore bodies in deep ocean sulfide deposits. Such surveys are known as 3D gravity surveys because we make measurements over a three dimensional region, recording gravity as a function of latitude, longitude, and height.

Figure 1: During the summer of 2009, a seafloor gravity survey was done over the Sleipner CO2 sequestration reservoir in the North Sea. A 100 m thick layer of sandstone, capped by an impermeable layer of shale, lies a km beneath the seafloor. On a nearby natural gas production platform, CO2(which comprises 10% of the extracted gas) is separated from the produced hydrocarbon and re-injected into the sandstone layer, where we hope it will remain for eternity. To confirm this expectation, gravity is monitored as a function of time on the seafloor. Shown in this photo is a Remotely Operated Vehicle (ROV) which sets our gravity meters (seen held in the ROV’s manipulator arms) on an array of seafloor benchmarks. These benchmarks are reoccupied by the gravity meters every few years.

Gravity also can change with time at a given location if the density of the underlying rock changes. This makes it useful for monitoring the evolution of an oil or gas reservoir. Normally, as hydrocarbons are extracted from a reservoir beneath the seafloor, water gradually flows in to replace the extracted oil or gas. Because its density is different from that of the fluid it has replaced, gravity changes observed above the reservoir reveal the spatial pattern of water influx. This is important information that is utilized for planning future production. Such gravity surveys are known as 4D surveys because the dimension of time is included.

We are applying this method in reverse in a large scale CO2 sequestration experiment. A million tons of CO2 have been injected annually over the past decade into a reservoir beneath the Sleipner platform in the North Sea. Repeated gravity measurements over the reservoir reveal the density of the sequestered CO2, which replaces water in the pore spaces. Over time, a leak in the reservoir would cause the fit of the gravity measurements to no longer match the model of the known amount of injected CO2.

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Figure 2. Results showing the difference in gravity observed in 2002 from the values obtained in the 2009 survey of 30 benchmarks spread out over a 10 km region overlying the reservoir (benchmarks 1 through 20 are arranged in a straight line crossing the reservoir). The gravity observations closely match the modeled carbon dioxide signal.


Eiken, O., T. Stenvold, M. Zumberge, H. Alnes, and G. Sasagawa (2008). Gravimetric monitoring of gas production from the Troll field, Geophysics, 73, WA149; doi:10.1190/1.2978166.

Institute of Geophysics and Planetary Physics, SIO/UCSD9500 Gilman Drive, La Jolla, CA 92093-0225

Geosciences Research Division, SIO/UCSD9500 Gilman Drive, La Jolla, CA 92093-0220

Web: sio.ucsd.edu/Research/Research_Units/Earth_Science

Image: Sea-ice and icebergs off the East Antarctic coast

between Davis station and the Amery Ice Shelf. The photo

was taken by James Behrens (IGPP) while he was working

with Helen Fricker to deploy seismometers and GPS on the

Amery Ice Shelf.

full rpt-2010 cvr - scripps institution of oceanographytigators in the earth section over...

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