delineating)paleoseismologicalfeatures...

82nd Annual Meeting of the Eastern Section of the Seismological Society of America October 18-‐19, 2010

DELINEATING PALEOSEISMOLOGICAL FEATURES USING GROUND PENETRATING RADAR AND CAPACITIVELY COUPLED RESISTIVITY

AL-‐QADHI, Okba, MAHDI, Hanan, AL-‐SHUKRI, Haydar, Applied Science Department, University of Arkansas at Little Rock, Little Rock, AR 72204, TUTTLE, Tish, M. Tuttle & Associates,128 Tibbetts Lane, Georgetown, ME 04548

Abstract: Satellite images and field surveys reveal the existence of several earthquake-‐induced liquefaction features in east-‐central Arkansas in an area not previously known to have experienced major earthquakes in the past. Sand blows and feeder dikes were mapped with ground penetrating radar (GPR) using a 400MHz central frequency monostatic antenna with a high-‐speed acquisition system and capacitively coupled resistivity (CCR) with different transmitter and receiver spacing intervals. GPR and CCR surveys were performed along profiles tens of meters to hundreds of meters in length and over the same areas to independently verify the location of liquefaction features. This implementation allowed us to image, in three dimensions, sand blows and feeder dikes and related ground subsidence as well as to track for 17 km a northwest-‐oriented lineament delineated by sand blows. Both techniques were instrumental in locating feeder dikes of sand blows and visualizing the contact between sand blows and the buried paleosurfaces. The most prominent anomalies in both GPR and resistivity data correlate with the breach of the silt loam layer indicative of sand dikes. In some cases, resistivity is superior to GPR for imaging sand blows and sand dikes, especially when the sediment is wet. Due to the deeper penetration of electric current, the resistivity method can reveal deeper information than the GPR technique. In addition, CCR is better at identifying the boundaries of sand blows than GPR. On the other hand, GPR is able to precisely locate the feeder dikes, which is an essential step for citing trenches for paleoseismic study of the liquefaction features. The results support using resistivity in combination with GPR to map liquefaction features.

Presentation Type: Oral

Presenting Author: Okba Al-‐Qadhi

7


Paper Withdrawn

EARTHQUAKE EARLY WARNING SYSTEM FOR IRAN

AMIRNEZHAD MOZHDEHI, Sahar, ZARE, Mehdi, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran, [email protected]

Abstract: Iran is a seismically active region and both historic and instrumental records indicate the occurrence of many devastating seismic events, especially in densely populated areas which are located in the vicinity of major faults. Tehran, the capital of Iran, for example, accommodates nearly 10,000,000 people and is surrounded by many active faults (Mosha, North Tehran, Kahrizak…). Therefore, an earthquake early warning is an appropriate short term solution to reduce losses of a probable large earthquake. As of seismic instrumentation, three major seismic networks are operating which need serious development and integrity. Iran Strong Motion Network (ISMN) was founded in 1973 (with less than 300 analog accelerographs), and was extended in 1993 by installation of digital accelerographs (over 1000 in 2007), but only 50 stations use GPS timing. Iranian National Seismic Network (INSN) includes 30 real-‐time broadband stations. The Iranian Seismic Telemetry Network was founded in 1995 with 70 3-‐component seismographs (mostly short-‐period and occasionally broadband) which are in real-‐time connection with processing center. Expectedly, the available seismic records are sometimes of poor quality (due to low network density) and mostly lack absolute timing. To optimize the use of accessible data, a method should be used which is capable of using both single-‐station and multi-‐station data, so that we can make the best use of existing data. Therefore, a combination of Elarms and tau-‐c Pd methods is chosen for this area. At the end, the results can be used to optimize and modify the existing seismic networks to form an earthquake early warning system for important cities, especially Tehran.

Presentation Type: Poster

Presenting Author: Sahar Amirnezhad Mozhdehi

8


EARTHSCOPE TRANSPORTABLE ARRAY (TA) PLANS FOR EASTERN NORTH AMERICA

BUSBY R.W., HAFNER K., WOODWARD R., Incorporated Research Institutions for Seismology (IRIS)Washington DC 20005 USA [email protected]

Abstract: The Transportable Array (TA) element of Earthscope / US Array is a large deployment of 400 high quality broadband seismographs. The Transportable Array is operated by the IRIS Consortium, and is part of the EarthScope Project sponsored by the National Science Foundation. The construction of this array began in October 2003 and the full deployment of USArray TA is now continuously rolling from west to east across the continental US. This requires the installation (and removal) of approximately 18 stations each month for a ten year period. The TA has now occupied over 1000 sites in the western United States and is midway through its multiyear migration to reach the last installation in the Eastern North America in Sept 2013.

The USArray portion of the EarthScope Project was recently authorized by the National Science Foundation to plan deployment of about 50 stations in the Ontario and Quebec Provinces of Canada. These locations would supplement existing seismic stations operated by Geological Survey of Canada and the POLARIS project to form a uniform 70km grid of stations south of 47 degrees latitude. The deployment is contingent upon continued execution of the TA throughout the continental US on schedule and budget. We will be soliciting university and student assistance in siting stations and refining locations with any partners that might yield permanent stations.


Presenting Author: Robert Busby

9


FINITE-FAULT MODEL SIMULATIONS FOR INSIGHT INTO NEAR-SOURCE GROUND MOTIONS IN EASTERN NORTH AMERICA

CHAPMAN, Martin C., Department of Geosciences, Virginia Tech, Blacksburg, VA, 24061, [email protected]

Abstract: A full wavefield finite-‐fault simulation method is being used to explore the nature of ground motion near the earthquake source, with particular focus on path and site conditions found in eastern North America. Among the issues being investigated by modeling is the nature of the vertical component at near-‐fault distances, in terms of the rate at which amplitudes decay with distance (apparent geometrical spreading) and dependence on crustal structure, focal depth and focal mechanism. The vertical component is of particular interest because it has received relatively little attention from the earthquake engineering community. The existing world-‐wide strong motion data set shows that vertical amplitudes are usually less than horizontal at frequencies of primary engineering concern. But even the world-‐wide data base is sparse for sites within a few kilometers of the rupture, particularly so for data collected at locations with geological conditions prevalent in eastern North America. Most structural dynamic models indicate that structural elements are most vulnerable to the horizontal ground motions: vertical motions appear to have a relatively minor contribution to structural damage. However, non-‐structural components may be sensitive to vertical motions, particularly at high frequency. This may be important for near-‐source rock sites in eastern North America as well as for sites with soil/sediment overlying high-‐velocity basement. In the former case, maximum vertical amplitudes near the source appear to be associated with a large amplitude SV arrival, whereas in the latter, unusually efficient S to P conversion at the basement interface and near-‐vertical ray incidence at the surface may contribute to large vertical motions.


Presenting Author: Martin Chapman

10


THE NEW MADRID 1811-1812 MAINSHOCKS: M6S OR M7S?

CRAMER, Chris H., and DANGKUA, Donny, CERI, University of Memphis, Memphis, TN, 38152-‐3050, USA, [email protected]

Abstract: Dangkua and Cramer (2010) reevaluated the ground motion verses intensity relations of Kaka and Atkinson (2004) and Atkinson and Kaka (2007), which reached opposing conclusions as to whether eastern North America (ENA) and California (CA) relations are different or the same. We concluded that at short periods (pga, 0.3 s Sa) ENA and CA ground motion vs. intensity relations are the same, but at longer periods (pgv, 1.0s and 2.0s Sa) they are different due to differences in ENA and CA source spectral shapes. Recently, intensities (MMIs) for the three New Madrid mainshocks were reevaluated and their magnitudes proposed to be high M6s (M6.8). We apply ENA ground motion prediction equations (GMPEs) to New Madrid scenario ruptures, make adjustments for local site geology, and estimate MMI from 1.0s Sa scenarios using the Dangkua and Cramer (2010) relations. The GMPEs applied are those of the 2008 USGS national seismic hazard maps, including weights. Local geology effects were taken into account using the surface soil geology, soil thickness, and relevant Vs reference profiles. For the December 16, 1811 mainshock, a comparison of M7.7 and M6.8 scenario estimates of MMI to the observed MMIs suggests that the 1811-‐1812 New Madrid mainshocks are more likely M7s and not M6s, within uncertainty. Further refinements of the scenario MMI models are needed to (1) extend ground motion estimates and hence MMI estimates beyond the current 1000 km distance limit, (2) improve spatial resolution to less than 10 km to better resolve MMIs in major river valleys, and (3) quantify the goodness-‐of-‐fit of the estimates to the observations so the confidence in these conclusions can be improved.


Presenting Author: Chris Cramer

11


GROUND MOTION PREDICTION TRENDS FOR EASTERN NORTH AMERICA BASED ON THE NEXT GENERATION ATTENUATION EAST GROUND MOTION DATABASE

CRAMER, Chris H., KUTLIROFF, Jerome, and DANGKUA, Donny, CERI, University of Memphis, Memphis, TN 38152-‐3050, USA, [email protected]

Abstract: A five-‐year Next Generation Attenuation (NGA) East project to develop new ground motion prediction equations for stable continental regions (SCRs), including eastern North America (ENA), has begun at the Pacific Earthquake Engineering Research (PEER) Center funded by the Nuclear Regulatory Commission (NRC), the U.S. Geological Survey (USGS), the Electric Power Research Institute (EPRI), and the Department of Energy (DOE). The initial effort focused on database design and collection of appropriate M>4 ENA broadband and accelerograph records to populate the database. Ongoing work has focused on adding records from smaller ENA earthquakes and from other SCRs such as Europe, Australia, and India. Currently, over 6500 horizontal and vertical component records from 60 ENA earthquakes have been collected and prepared (instrument response removed, filtering to acceptable-‐signal band, determining peak and spectral parameter values, quality assurance, etc.) for the database. Geologic Survey of Canada (GSC) strong motion recordings, previously not available, have also been added to the NGA East database. The additional earthquakes increase the number of ground motion recordings in the 10 – 100 km range, particularly from the 2008 M5.2 Mt. Carmel, IL event, and the 2005 M4.7 Riviere du Loup and 2010 M5.0 Val des Bois earthquakes in Quebec, Canada. The goal is to complete the ENA database and make it available in 2011 followed by a SCR database in 2012. Comparisons of ground motion observations from four recent M5 ENA earthquakes with current ENA ground motion prediction equations (GMPEs) suggest that current GMPEs, as a group, reasonably agree with M5 observations at short periods, particularly at distances less than 200 km. However, at one second, current GMPEs over predict M5 ground motion observations. The 2001 M7.6 Bhuj, India, earthquake provides some constraint at large magnitudes, as geology and regional attenuation is analogous to ENA. Cramer and Kumar, 2003, have shown that ENA GMPE’s generally agree with the Bhuj dataset within 300 km at short and long periods. But the Bhuj earthquake does not exhibit the intermediate-‐period spectral sag (Atkinson, 1993) of larger ENA earthquakes and thus the Bhuj ground motions may be larger than what could be expected at one second for M7s in ENA.


Presenting Author: Chris Cramer 12


THE APPLICATION OF VELOCITY SPECTRAL STACKING METHODS TO DETERMINE THE SOURCE SPECTRA AND SCALING RELATIONS FOR SMALL TO MODERATE EARTHQUAKES IN SOUTHERN ONTARIO/WESTERN QUEBEC

DINEVA, Savka, Queens University, Kingston, Ontario, K7L 3N6, [email protected]; MEREU, Robert, University of Western Ontario, London, Ontario, N6A 5B7, [email protected]; ATKINSON, Gail, University of Western Ontario, London, Ontario, N6A 5B7,[email protected]

Abstract: We analyzed the spectra from 370 earthquakes of energy magnitude (ME) 1.1 to 5.8 recorded by the Southern Ontario Seismic Network (SOSN) /POLARIS network during the period 1991-‐2010 in the area of southern Ontario and western Quebec. The energy magnitude is based on the square root of the time-‐domain signal energy (Dineva and Mereu 2009). Over 3000 S-‐wave spectra were processed, and used to determine corner frequencies, scaling and attenuation relationships for the region. Several factors that affect observed spectra were considered in this study: the attenuation of seismic waves, the station site response, random scattering effects, and the magnitude of the earthquakes. Examination of individual attenuation-‐corrected spectra revealed a lot of complexity from station to station for the same event which made the direct determination of corner frequencies problematic. However stacking of the velocity spectra into magnitude bins removed most of the complexity to reveal a well imaged source spectrum each with a clear maximum. Some of the bins for a single magnitude contained more than 250 spectra. The corner frequency for each of the stacked spectra was calculated by fitting to a theoretical Brune (omega-‐squared) spectra. We obtained a very well-‐constrained linear relationship (slope approximately -‐0.22) between log (corner frequency) and energy magnitude. This relation was then used to determine scaling relations between a number of quantities such as energy magnitude, moment magnitude, seismic moment and stress drop. Our results also clearly show that the earthquakes in the magnitude range (1.5-‐4.5) in our study region are not self-‐similar.


Presenting Author: Robert Mereu

13


DETERMINING FOCAL DEPTHS OF EARTHQUAKES IN THE NORTHEASTERN U.S. AND SOUTHEASTERN CANADA

DOUGHERTY, Laura B., EBEL, John E., Weston Observatory, Department of Geology and Geophysics, Boston College, Weston, MA 02493 USA

Abstract: Many shallow, small-‐to-‐moderate earthquakes occur throughout the Northeastern U.S. and Southeastern Canada. The goal of this research is to create a method to verify the depths of local earthquakes by analyzing the arrival times of depth phases sP and pP in the P waveforms generated by earthquakes in the Northeastern U.S. and Southeastern Canada. This is important because for the area of interest, New England, New York, New Jersey and Southeastern Canada (Quebec and Ontario), the seismic networks have sparsely distributed stations, increasing the difficulty of accurately determining focal depths of local earthquakes using the arrival times of P and S wave.. Crustal models that are used to locate earthquakes in the region were created to determine the arrival times of these depth phases. One earthquake of focus is the magnitude 4.9 earthquake that occurred on June 23, 2010, 64 kilometers north-‐northeast of Ottawa, Ontario. The hypocentral solution computed for this earthquake by the Canadian Geological Survey is 19.3 kilometers. The P waveforms for this earthquake were analyzed by computing the estimated arrival times of the phases Pn, sP and pP for this earthquake from several seismic stations in order to see if the depth phases pP and sP could be identified. To try to enhance the possibility of observing these depth phases, the P waveforms were aligned at the P first arrival time and then stacked in order to see if the depth phases pP and sP become more identifiable. The stacking did not bring out strong depth phases, perhaps due to radiation pattern effects. A similar kind of analysis is being carried out for the depth phases for other earthquakes in the region in order to determine the utility of routinely using depth phases to find the hypocentral depths of earthquakes in the region.


Presenting Author: Laura Dougherty

14


REAL-TIME SEISMIC MONITORING OF AFTERSHOCKS OF THE 2010 HAITI EARTHQUAKE

DRYSDALE, J. A.; BENT, A. L.; HALCHUK, S.; ADAMS, J.; GREENE, H.; PROULX, F.; MCCORMACK, D. A.; AL-‐KHOUBBI, I.; ANDREWS, C.; ASUDEH, I.; BELIZAIRE, D.; and DORFEUILLE, H.

Abstract: Following the devastating earthquake in Haiti on January 12, 2010, the need for improved local monitoring of the seismic activity in that country become apparent. The Geological Survey of Canada, Natural Resources Canada, installed what is believed to be the first continuously transmitting seismograph network in Haiti. Three semi-‐permanent stations are installed at Port-‐au-‐Prince, Jacmel and Léogâne. Each station consists of a three-‐component broadband seismograph and a three-‐component strong-‐motion instrument. The strong-‐motion instruments have proven useful in providing clear records in cases where some of the largest aftershocks were clipped on the weak-‐motion channels. Continuous data are transmitted by satellite in real time to Ottawa for analysis. Data are also forwarded to the United States Geological Survey and the Caribbean Tsunami Warning System. Early analysis of the data has focused primarily on locating aftershocks with the expectation that longer term monitoring will result in improved seismic hazard assessments for Haiti. All aftershock locations and phase picks are forwarded to the International Seismological Centre. Magnitude recurrence curves show that the aftershock catalog is complete to magnitude 2.6. The majority of the aftershocks are located just north of the peninsula. The station geometry is not ideal for locating aftershocks. Combining our data set with that of other stations deployed in the region following the main shock should result in improved locations and better depth control. Focal mechanisms have been determined for many of the aftershocks by regional moment tensor inversion for large aftershocks and by composite first-‐motion solutions for smaller aftershocks. Both methods show predominantly thrust faulting at the western end of the aftershock zone and strike-‐slip faulting in the east, consistent with the global moment tensor solutions for the main shock and largest aftershock. Depths from the moment tensor inversion range from 2 to 15 km, with the majority of the events occurring between 6 and 10 km. Teleseismic receiver functions are being employed to derive improved velocity models for Haiti. Results to date are indicative of low near-‐surface velocities and a Moho depth of approximately 20 km.


Presenting Author: Janet Drysdale 15


A DATABASE OF HISTORICAL EARTHQUAKES OF THE NORTHEASTERN U.S. AND SOUTHEASTERN CANADA

EBEL, John E., and DUPUY, Megan, Weston Observatory, Department of Geology and Geophysics, Boston College, Weston, MA 02493 USA, [email protected]

Abstract: A project has begun at Weston Observatory to create a database of information on historical earthquakes of the northeastern U.S. and nearby southeastern Canada. Unlike earlier flat-‐file earthquake catalogs, this will be a relational earthquake database that will include all available information about the earthquakes, including hypocentral estimates, damage and felt reports, MMI estimates for each report, magnitude estimates, etc. Original historical sources will be scanned and incorporated into the database. Over 180 separate fields are currently planned for the database in the following general categories: date-‐time, historical accounts, hypocenter, maximum ground motion, magnitude-‐moment, intensity, casualties-‐homeless, liquefaction-‐landslide-‐tsunami, focal mechanism, fault information, other source parameters. The database is being designed with an interface so that it can be interrogated by use of a web browser. An interface for input of information into the database has been designed and is currently being tested. So far, about 450 accounts of earthquakes, including publication notes, have been transcribed for the database. For all earthquakes, primary sources concerning the events are being procured and included in the database along with derived parameters such as hypocenter, magnitude, seismic moment, modified-‐Mercalli intensity, etc. The sources for the derived event parameters are being input as part of the database, and uncertainties in the event parameters are also included in the database. New information about earthquakes in the database can be easily added in the future as it becomes available.


Presenting Author: Megan Dupuy

16


ASSESSING THE MAGNITUDE OF THE OCTOBER 20, 1870 CHARLEVOIX, QUEBEC EARTHQUAKE

EBEL, John E., DUPUY, Megan, Weston Observatory, Department of Geology and Geophysics, Boston College, Weston, MA 02493 USA, [email protected], and BAKUN, William H., U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025, USA

Abstract: One of the strongest historic earthquakes in the Charlevoix, Quebec seismic zone took place on October 20, 1870. This earthquake was most damaging at Baie-‐Saint-‐Paul, Saint-‐Urbain, Ile au Coudres and Les Eboulements in Quebec, and it caused two casualties at Les Eboulements. The earthquake was felt throughout much of southeastern Canada and along the U.S. Atlantic seaboard from Maine to Maryland. Site-‐specific damage and felt reports from U.S. cities and towns were obtained from newspaper accounts of the earthquake, and modified Mercalli intensity (MMI) values were assigned to each account where possible. This U.S. MMI dataset was then combined with an MMI dataset for this event from Canada. The combined MMI data were used in a Bakun and Wentworth analysis of the location and magnitude of the earthquake. From this analysis, the macroseismic center of the earthquake is determined to be very close to Baie-‐Saint-‐Paul, where the greatest damage was reported, and the intensity magnitude MI is found to be 5.8, with a range of 5.5-‐6.0. Comparisons were made at common sites of the MMI data for the 1870 earthquake and for the M 6.2 Charlevoix earthquake of 1925. On average the MMI readings are about .5 magnitude units smaller for the 1870 earthquake than for the 1925 earthquake, suggesting that the 1870 earthquake was M 5.6-‐5.7 after corrections for epicentral distance differences have been applied to the MMI differences. A similar comparison of the MMI data for the 1870 earthquake with the corresponding data for the M 5.9 1988 Saguenay suggests that the 1870 earthquake was M 5.9-‐6.0. These analyses indicate that the 1870 Charlevoix earthquake was M 5.5-‐6.0, with a best estimate of M 5.8.


Presenting Author: John Ebel

17


RESOLVING LATERAL VARIATIONS IN UPPER MANTLE STRUCTURE OF EASTERN NORTH AMERICA: AN OPPORTUNITY FOR USARRAY

EBEL, John E., Weston Observatory, Department of Geology and Geophysics, Boston College, Weston, MA 02493 USA, [email protected]

Abstract: There are strong lateral and vertical variations in the Moho and the velocity structure of the uppermost mantle beneath northeastern North America. Along coastal New England, which is composed of exotic terranes that accreted onto North America during Paleozoic and early Mesozoic time, the Moho is a sharp interface at a depth of about 30 km. Inland from the coast, the Moho deepens in two steps to western Maine, where it is 38-‐40 km deep and is a gradational interface. In Quebec, which is part of the Grenville province of the North American craton, the Moho is a relatively sharp interface at a depth of about 42 km. Beneath New England the sub-‐Moho velocity is about 8.12 km/sec and has no increase with depth down to about 60 km. On the other hand, beneath southern Quebec the sub-‐Moho velocity is about 8.23 km/sec and increases to about 8.5-‐8.6 km/sec at about 60 km depth. Details of the spatial variations of the uppermost mantle velocities are lacking in the current data that exist for this region. A focused Earthscope experiment is needed to get a high resolution image of the depth to the Moho, of the character of the Moho interface (sharp boundary versus gradational interface) and of the change of velocity with depth in the uppermost mantle below the Moho across the northern and southern Appalachians. Such an experiment would make use of data from USArray as well as from some high-‐density seismic lines both across and along the Appalachians where refraction and receiver function data would be acquired. A high-‐resolution image of the Moho and upper mantle would reveal important structural details to constrain models of the assembly of the exotic terranes onto the east coast of North America. It could also provide important insights into the structures that are associated with the seismicity of the eastern U.S. and southeastern Canada.


Presenting Author: John Ebel

18


THE JUNE 23, 2010 MW 5.0 VAL-DES-BOIS, QUEBEC EARTHQUAKE

HAYEK, Sylvia, HALCHUK, Stephen, DRYSDALE, Janet, LIN, Lan, PECI, Veronika, ADAMS, John, PROULX, Frederic, BENT, Allison, ASUDEH, Isa, Canadian Hazards Information Service, Natural Resources Canada, 7 Observatory Cres., Ottawa, ON K1A 0Y3

Abstract: On June 23, 2010 at 17:41 U.T., a magnitude Mw 5.0 (mN 5.7) occurred approximately 10 km southeast of Val-‐des-‐Bois, Quebec within the West Quebec seismic zone. It was one of the largest recent events to have occurred in eastern Canada. Due to its size and proximity to Ottawa (~55 km), this earthquake produced the strongest shaking ever felt in Ottawa. It was widely felt in eastern Canada (from Thunder Bay to Nova Scotia) and into the northeast United States, and as far away as Kentucky. Over 5000 felt reports were entered via the EarthquakesCanada website. There was light damage in Ottawa (mostly to chimneys and contents) and similar damage in the epicentral region (but also including failure of a bridge embankment and two large landslides in clay). The main event was well recorded by strong and weak motion instruments. A maximum PGA of ~8-‐10 %g was recorded by strong motion instruments in the Ottawa region, and 0.8% g in Montreal. Together with data from 11 weak-‐motion stations (at epicentral distances 20-‐160 km) these show that the shaking in Ottawa was well below the 1/2475 year design spectra in the 2005 National Building Code of Canada. The estimated return period for the shaking is ~150 years.

Analysis of the main shock indicates a focal depth of 22 km, with a predominantly thrust mechanism on planes trending northwest-‐southeast. These findings are consistent with the parameters of most other Western Quebec earthquakes. Seven aftershock instruments were deployed in the epicentral region within 24 hours, including one real-‐time, continuous 6-‐component station VDBQ. More than 250 aftershocks above M1 have been recorded since June 23, six above magnitude 3, the largest of which was a mN 3.3 on June 23 at 23:34 UT.


Presenting Author: Janet Drysdale

19


SEISMIC REFRACTION ANALYSIS OF THE UPPER MANTLE PN WAVE THROUGH NORTHEASTERN NORTH AMERICA

HERTZOG, Justin T., EBEL, John E., Boston College Department of Geology and Geophysics, Chestnut Hill, MA 02467 [email protected]

Abstract: Previous seismic studies have shown laterally varying P-‐wave seismic structures in the uppermost mantle throughout northeastern North America. Using the seismic refraction technique new data from 1992 to the present are analyzed to delineate with improved spatial resolution the upper mantle P-‐velocity structure throughout the Avalon, northern Appalachians, and Grenville terranes of the northeastern US and southeastern Canada. A total of one hundred and sixty-‐eight earthquakes are being analyzed, utilizing over one hundred seismic stations throughout northeastern North America. The uppermost mantle P-‐wave velocity structure is best resolved horizontally from the seismic data in southeastern Canada Grenville terrane and the Avalon terrane in southeastern parts of New England. Data analyzed between 200 -‐ 400 km, 400 -‐ 600 km, and 600 + km throughout these regions are used to study the increase in velocity with depth in the upper mantle. The P-‐wave velocity of the upper mantle Moho through the Avalon terrane in southeastern New England is found to be uniformly 8.1 – 8.2 km/s in this study for epicentral distances of 200 km to 800 km. No increase in velocity with depth is recognized in the New England region. Pn velocities throughout the Grenville terrane show an average velocity of 8.15 km/s to 8.6 km/s as epicentral distance increases. A jack-‐knife analysis was completed and puts constraints on the uncertainties of the velocity measurements. For these distances the velocities for southeastern Canada are 8.28, 8.27, 8.60 km/s and for New England the velocities are 8.16, 8.22, 8.11, km/s respectively. Uncertainties though these areas range from 0.012– 0.20 km/s.


Presenting Author: Justin Hertzog

20


CELLULAR SEISMOLOGY AND SEISMIC SOURCE CHARACTERIZATION OF THE CENTRAL AND EASTERN UNITED STATES

KAFKA, Alan L., Weston Observatory, Department of Geology and Geophysics, Boston College, Weston, MA, 02493

Abstract: Past seismicity is often used as a significant component of seismic source characterization (SSC) in intraplate regions, such as the central and eastern United States (CEUS), where geology does not typically provide clear evidence of potential locations of future earthquakes. Using past seismicity for this purpose, however, is only scientifically justified if the tendency for past seismicity to delineate potential locations of future earthquakes is well-‐established as a real, measurable, physical phenomenon. If not, then this presumed tendency has no scientific basis as a means of characterizing seismic sources. To explore these issues, this study builds upon the results of Kafka (2002, 2007) to further investigate the scientific basis underlying the use of past seismicity for SSC in the CEUS. The USGS National Seismic Hazard maps use Gaussian Smoothing (GS) to map the spatial distribution of past seismicity in the CEUS. In this study, I compare Cellular Seismology (CS) with GS as a method of mapping the spatial distribution of past seismicity in the CEUS, and I evaluate each method's rate of success for forecasting earthquake locations. CS is a simple method that considers a location to be a potential source point of future earthquakes even if only one past earthquake occurred near that point. For the cases analyzed here, CS appears to predict the locations of future earthquakes just as well as GS when both methods are applied to the same past seismicity catalog. For the equivalent percentage of map area covered by the past seismicity forecast, CS predicts some earthquakes to occur in places where GS doesn't. CS is simpler and based on less assumptions than GS. GS requires smoothing rates seismicity, declustering the earthquake catalog to remove dependent events, and deciding what parameters to use for the smoothing. CS does not require any of these complications, yet it appears to forecast the locations of future earthquakes just as well as GS.


Presenting Author: Alan Kafka

21


CODA Q (QC) ESTIMATES IN THE NORTH EAST (NE) INDIA USING LOCAL EARTHQUAKES

KUMAR, Mohapatra Alok, Research Scholar, Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, West Bengal, India. Email: [email protected]; KUMAR, Mohanty William, Associate Professor, Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, West Bengal, India. Email:[email protected]

Abstract: The quality factor of coda waves (Qc) has been estimated for the Northeastern (NE) India, using the digital data of ten local earthquakes from April 2001 to November 2002. The time domain coda decay method of a single back scattering model is used to calculate frequency dependent values of Coda Q (Qc). The earthquakes with magnitude range 3.8 to 4.9 have been used for estimation Qc at six central frequencies 1.5, 3.0, 6.0, 9.0, 12.0, and 18.0 Hz. These earthquakes are well recorded on the broad band seismic observatory of NE India located at Cherrapunji, Barapani and Bahiata. In the present work the Qc value of local earthquakes are estimated to understand the attenuation characteristic and tectonic activity of the region. Based on a criteria of homogeneity in the geological characteristics and the constrains imposed by the distribution of available events the study region has been divided into three zones such as the Tibetan Plateau Zone (TPZ), Bengal Alluvium and Arakan-‐Yuma Zone (BAZ), Sillong Plateau Zone (SPZ). It follows the power law Qc= Q0 ( f /f0) n where, Q0 is the quality factor at the reference frequency (1 Hz) f0 and n is the frequency parameter which varies from region to region. The mean values of Qc reveals a dependance on frequency, varying from 292.9 at 1.5 Hz to 4880.1 at 18 Hz. Average frequency dependent relationship Qc values obtained of the NE India is 198 f 1.035, while this relationship varies from the region to region such as, TPZ : Qc= 226 f 1.11, BAZ : Qc= 301 f 0.87, SPZ : Qc= 126 f 0.85. It indicates NE India is seismicaly active but comparing of all zones in the study region the Shillong Plateau Zone, Qc= 126 f 0.85 is seismicaly most active. Where as the Bengal Alluvium and Arakan-‐Yuma Zone are less active and out of three the Tibetan Plateau Zone is intermediate active. This study may be useful for the seismic hazard assessment.

Key words: Coda wave, Lapse time, Single backscattering model and NE India.


Presenting Author: ALOK KUMAR MOHAPATRA

22


DEVELOPING A POST-EARTHQUAKE COMMUNICATIONS STRATEGY FOR SEISMOLOGISTS

LAMONTAGNE, Maurice, Natural Resources Canada, 615 Booth Street, Ottawa, ON, K1A 0Y3; malamont_@_nrcan.gc.ca; WYNNE, Jane, Natural Resources Canada, Box 6000, 9860 West Saanich Road, Sidney, B.C. V8L 4B2; [email protected]

Abstract: In the aftermath of a largely felt earthquake, it is the traditional role of seismologists to provide factual information on the event and its seismological context. In this paper, we suggest that seismologists make use of this Teachable Moment opportunity to provide earthquake preparedness and mitigation information to the population. If the earthquake has caused damage, the message conveyed by seismologists should be adapted to meet the needs of the population in the epicentral region and contact should be maintained. It should also send clear and positive messages that develop and maintain public's trust. With this strategy, seismologists can help attenuate post-‐earthquake public anxiety, relieving unnecessary anxiety and promoting positive preparation. The strategy aims at empowering the population in the epicentral region by making residents active rather than passive. The paper will present examples when this post-‐communications strategy was used following the year 2010 Haiti, Chile and Val-‐des-‐Bois, Qc, earthquakes. It will also present some communications challenges that seismologists may be confronted to, such as the possibility of strong aftershocks, unfounded rumors, and multiple sources of conflicting information.


Presenting Author: Maurice Lamontagne

23


WAVE FIELD CONTINUATION AND DECOMPOSITION FOR PASSIVE SEISMIC IMAGING UNDER DEEP UNCONSOLIDATED SEDIMENTS

LANGSTON, CHARLES A., Center for Earthquake Research and Information, University of Memphis, Memphis, TN 38152-‐3050, USA, [email protected]

Abstract: The coastal plains of the central and eastern United States contain deep sections of unconsolidated to poorly consolidated sediments. These sediments mask deeper crustal and upper mantle converted phases in teleseismic receiver functions through large amplitude, near-‐surface reverberations, and also amplify ambient noise levels to generally reduce data signal-‐to-‐noise ratios. Removing shallow sediment wave propagation effects is critical for imaging deep lithospheric structure. A propagator matrix formalism is used to downward continue the wave field for teleseismic P waves into the mid-‐crust in order to separate the upgoing S wave field from the total teleseismic response of the P wave, exposing deep Sp conversions. This method requires that the earth model from the surface to the reference depth be known. Teleseismic P wave data for the Memphis, TN, station (MPH) are analyzed using a reference station deconvolution technique to produce vertical and radial P wave transfer functions. These transfer functions are modeled using a simple model parameterization for sediment structure through grid inversion. The inversion earth model is incorporated into the wave field continuation and decomposition technique to estimate the up-‐going S wave field at 10 km depth in the crust. Moho and possible deeper Ps conversion are identified with this process.


Presenting Author: Charles Langston

24


MICROTREMOR SURVEYS CROSSING THE CONNECTICUT RIVER VALLEY

LIU, Lanbo, WHITE, Eric, URIN, Fatih, and ROHRBACH, Eric, Department of Civil and Environmental Engineering, University of Connecticut, Storrs, CT 06269, USA, [email protected]

Abstract: For assess the soil property and the thickness of the sediments in the greater Hartford area we have conducted a number of microtremor surveys crossing the Connecticut River Valley centered at Hartford, Connecticut. The backbone part of these surveys was a 26-‐mile long profile conducted along the east-‐west running Route 44 from the town of Canton on the Western Highland of the Valley to Bolton Notch on the Eastern Highland of the River Valley. Along this profile there are 10 sites have been occupied, with a station spacing of approximately 2 miles. The instrument used to acquire the data is the Gulrap 3-‐component broadband seismometer and the sampling frequency is 40 Hz. At each site the observation period is no less than 30 minutes with the maximum observation time at Avon, CT for more than 2 hours. In addition, we have also carried a more concentrated microtremor survey on the Connecticut River bank in the Haddam Meadows state park with both the Gulrap seismometer and a 48-‐channel engineering seismometer with 4.5 Hz vertical and horizontal geophones. The preliminary results shows the thickest sediments located east of the Connecticut River in the town of East Hartford. The concentrated survey at Haddam Meadows has shown the sediment-‐bedrock depth is about 40 meter, in a good agreement with the well-‐logging information on the same site. Microtremor surveys provide an economical supplement to traditional boring and coring of soil samples through drilling, an optimistic combination of the microtremor survey and traditional drilling will provide geotechnical engineers a more cost-‐effective tool in engineering site characterization.


Presenting Author: Lanbo Liu

25


CRUSTAL AND MANTLE STRUCTURE AND DYNAMICS BENEATH EASTERN NORTH AMERICA: ANTICIPATING THE ARRIVAL OF USARRAY

LONG, Maureen D., Department of Geology and Geophysics, Yale University, New Haven, CT, 06520; BENOIT, Margaret H., Department of Physics, The College of New Jersey, Ewing, NJ, 08628; CHAPMAN, Martin C., KING, Scott D., Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061

Abstract: The migration of the Transportable Array component of USArray represents an unprecedented opportunity to study the structure and evolution of the eastern US continental margin, and preparations for its arrival are underway. These include both the framing of important science questions and preparatory studies using existing seismic data. We describe two recent studies that have investigated the structure and dynamics of the eastern US in advance of the TA’s arrival. In the first study, we used data from permanent stations in the southeastern US to investigate the character of mantle flow beneath the passive margin. A variety of models for this flow field have been proposed, including those that invoke return flow from the sinking Farallon slab, small-‐scale convective downwelling at the edge of the continental root, or the upwards advective transport of volatiles from the deep slab through the upper mantle. We used shear wave splitting observations and receiver function analysis at broadband stations to test these proposed scenarios. SKS observations support a model in which there is a transition in the geometry of mantle flow from the continental interior to its edge, but the receiver function results do not unequivocally support transition zone thickening due either to cold downwelling or to widespread hydration. In the second study, we deployed a network of 9 broadband stations in a linear transect from coastal North Carolina to Ohio from 2009-‐2010, comprising the Test Experiment for Eastern North America (TEENA). The array was designed to probe the transitions in crustal and mantle structure and dynamics from the coast across the Appalachian orogenic province. We find evidence for sharp transitions in both crustal thickness and shear wave splitting behavior across the array. We expect that the necessary data to further constrain models for crustal evolution and mantle dynamics will be obtained from USArray in the near future.


Presenting Author: Maureen Long

26


UNCERTAINTY IN SEISMIC RISK ASSESSMENT

MALHOTRA, Praveen K., StrongMotions Inc., Sharon, MA 02067, USA, [email protected]

Abstract: Uncertainty is an integral part of risk. There cannot be risk without uncertainty but there can be uncertainty without risk. There is uncertainty in every step of seismic risk assessment: (1) uncertainty in time, location and size of earthquakes; (2) uncertainty in ground shaking due to a given earthquake; and (3) uncertainty in damage for a given level of ground shaking. All sources of uncertainty affect the risk. While it is important to consider all sources of uncertainty in risk assessment, it is equally important to reduce the uncertainty to improve the value of risk assessment. This presentation will demonstrate the relative role played by various sources of uncertainty and discuss ways to reduce the uncertainty in seismic risk assessment.


Presenting Author: Praveen Malhotra

27


GEOPHYSICAL ANALYSIS OF A POSSIBLE ACTIVE FAULT OUTSIDE THE NEW MADRID SEISMIC ZONE (NMSZ), WESTERN TENNESSEE, USA

MARTIN, J.J., Department of Geology and Geophysics, Boston College, Chestnut Hill, MA, 02467; TUTTLE, Martitia P., M. Tuttle & Associates, 128 Tibbetts Lane, Georgetown, ME, 04548; EBEL, J.E., Weston Observatory, Boston College, 391 Concord RD, Weston, MA 02493

Abstract: The New Madrid Seismic Zone (NMZS) is famous for producing the 1811-‐1812 earthquake sequence, including some of the largest (M >7.3) intraplate earthquakes within the North American Plate. In addition, there is geologic evidence that the NMSZ generated similar earthquake sequences during the Late Holocene. During the 1811-‐1812 earthquake sequence, as well as three prior events, strain apparently was distributed over three main faults within the NMSZ – the New Madrid North Fault, the Cottonwood Grove Fault, and the Reelfoot Fault. There is geological evidence to suggest that strain has been released in earthquakes along other faults outside the NMSZ proper. During a previous study, a possible fault southwest of Dyersburg, TN was hypothesized on the basis of unusual ground failure exposed in the cutbank of the Obion River. In the summer 2009, a refraction survey was conducted in the vicinity of the site of ground failure and across the lineament to determine if there is any near-‐surface faulting. However, the close proximity of the water table to the surface led to inconclusive results. A reflection survey was subsequently conducted summer 2010, the goal being to image layers beneath near-‐surface liquefied layers. Preliminary analysis of this data indicates possible displacements of layers at depths of 27 meters. Displacement in these layers would indicate the presence of a potential fault. The existence of such a fault outside of the NMSZ would have implications for the earthquake source model for this region.


Presenting Author: Jake Martin

28


CORRELATING NEAR-SOURCE ROCK DAMAGE FROM SINGLE-HOLE EXPLOSIONS TO SEISMIC WAVES

MARTIN, Randolph, III, BOYD, Peter, New England Research, Inc., 331 Olcott Drive, Ste L1, White River Junction, VT 05001, STROUJKOVA, Anastasia, LEIDIG, Mark, LEWKOWICZ, James, BONNER, Jessie, Weston Geophysical Corp., 181 Bedford St, Ste 1, Lexington, MA 02420, LIU, Lanbo, Physics Department, University of Connecticut, Storrs, CT 06269

Abstract: We conducted the Vermont Damage Experiment. Five single-‐hole explosions with yields ranging from 60.8 to 122.5 kg were detonated in homogeneous, low fracture density granite. Explosives with different velocities of detonation (VOD), including black powder (0.53 km/sec), heavy ANFO (4.8 km/sec), and COMP B (8.1 km/sec) were detonated to relate the VOD to seismic wave generation and extent of damage zones in the source region. The goal of the experiment was to quantify different levels of rock damage around the source and relate the seismic wave generation to the degree and distribution of damage and fragmentation.

Examination of the surface after the blast found no radial fractures produced by the COMP B explosions, while there were large fractures with displacement from the heavy ANFO and Black Powder shots. Examination of cores showed few native fractures in the pre-‐shot medium. Post-‐blast core was fragmented in the vicinity of the shot point. Large scale induced fractures developed for only short distances below the shot points. Density of the rock in the vicinity of the shot point decreased after the blast while the porosity increased. Laboratory-‐measured acoustic velocities of the rock decreased by greater than 20% near the shot point.

Over 120 seismic stations were deployed to record the explosions at distances between 5 m and 30 km. Analysis of the seismic waves showed distinct differences in amplitudes between the three shots of the equal yields, with the heavy ANFO and COMP B producing larger seismic wave amplitudes than the Black Powder at frequencies greater than 10 Hz. The slower VOD explosives (e.g., ANFO and Black Powder) produced larger amplitudes at frequencies below 8 Hz than COMP B. We will present the analysis of pre-‐ and post-‐shot corings and borehole imaging and to relate the microscopic and macroscopic damage caused by the explosions to the frequency-‐dependent differences in seismic wave generation. This research was sponsored by the Air Force Research Laboratory.


Presenting Author: Martin Randolph

29


DID THE BELLS RING IN BOSTON? MYTH, HISTORY AND THE NEW MADRID EARTHQUAKES.

MORAN, Nathan K. Center for Earthquake Research and Information, University of Memphis, Memphis, TN, 38152-‐3050

Abstract: The 1811-‐1812 sequence of earthquakes in the New Madrid seismic zone generated much attention at the time from newspapers and other sources because they were felt as far as the New England states. In this region the reports of local effects were intermingled with accounts from closer to the epicenter. During the passage of time, however, the accuracy of the accounts and the perception of events have become blurry. Modern retellings of the events with garbled information can lead to a mistaken perception of how the earthquakes occurred and cause the public to have inaccurate information.. Myths, both generated at the time and due to modern retellings, can obscure the real impact that the earthquakes had and continue to have on seismology and other fields that study their implications in the modern era. Historical research methods can be used to uncover these inaccuracies and help better inform the public and the scientific community. The story of the bells ringing in Boston is an example of an inaccurate account and the methods used to uncover it. The research method used can be applied to other accounts to test their validity.

The use of historical research methods can uncover further evidence about the earthquakes and even more crucially help to judge if these sources can be used reliably. Source information from the historic method has to be analyzed for its accuracy and importance before its use. What would be useful to a seismologist as information might be irrelevant to a historian or the reverse might be true. Basic historic research methods such as bibliographic and archival searching combined with databasing of information can yield new information that previously would have been undetected or misunderstood. Historic research maxims such as the use of primary source material that was created as soon as possible after the event in question can help to sort out the quality of information and its utility. Background research on the sources uncovered reveals if the source information is accurate or valid to the event being researched. Misuse of historic research can lead to inaccurate analysis of historic seismic events based on incorrect data. If historic data is used properly and with a contextual basis, it then can be a solid source of data for the analysis of pre-‐instrumental earthquakes.


Presenting Author: Nathan K. Moran

30


THE BOSTON COLLEGE EDUCATIONAL SEISMOLOGY PROJECT: INVITING STUDENTS INTO THE WORLD OF SCIENCE RESEARCH

MOULIS, Anastasia M., KAFKA, Alan, CAMPBELL, Leslie, EBEL, John, BIBEAU, Marilyn, Weston Observatory, Department of Geology and Geophysics, Boston College, Weston, MA, 02493; BARNETT, Michael, Lynch School of Education, Boston College, Chestnut Hill, MA, 02467

Abstract: The Boston College Educational Seismology Project (BC-‐ESP) operates an ed�u�c�a�t�i�o�n�a�l� �s�e�i�s�m�i�c� �n�e�t�w�o�r�k� �c�o�n�s�i�s�t�i�n�g� �o�f� �E�Q�1� �a�n�d� �A�S�1� �s�e�i�s�m�o�g�r�a�p�h�s� �l�o�c�a�t�e�d� �a�t� �K�-‐�1�2� �s�c�h�o�o�l�s� �i�n� �M�a�s�s�a�c�h�u�s�e�t�t�s�.� �E�Q�1� �a�n�d� �A�S�1� �s�e�i�s�m�o�g�r�a�p�h�s� �a�r�e� �a�l�s�o� �l�o�c�a�t�e�d� �a�t� �t�h�e� �B�o�s�t�o�n� �C�o�l�l�e�g�e� �c�a�m�p�u�s� �a�n�d� �W�e�s�t�o�n� �O�b�s�e�r�v�a�t�o�r�y� �a�s� �p�a�r�t� �o�f� �t�h�e� �B�C�-‐�E�S�P�.� �T�h�i�s� �p�r�o�j�e�c�t� �u�s�e�s� �s�e�i�s�m�o�l�o�g�y� �a�s� �a� �m�e�d�i�u�m� �f�o�r� �i�n�v�i�t�i�n�g� �s�t�u�d�e�n�t�s� �i�n�t�o� �t�h�e� �w�o�r�l�d� �o�f� �s�c�i�e�n�c�e� �r�e�s�e�a�r�c�h� �v�i�a� �i�n�q�u�i�r�y�-‐�b�a�s�e�d� �l�e�a�r�n�i�n�g� �t�h�r�o�u�g�h� �i�n�v�e�s�t�i�g�a�t�i�o�n� �o�f� �e�a�r�t�h�q�u�a�k�e�s� �r�e�c�o�r�d�e�d� �b�y� �s�e�i�s�m�o�g�r�a�p�h�s� �i�n� �K�-‐�1�2� �c�l�a�s�s�r�o�o�m�s�.� �S�i�n�c�e� �s�e�i�s�m�o�l�o�g�y� �i�s� �a�n� �i�n�t�e�r�d�i�s�c�i�p�l�i�n�a�r�y� �s�c�i�e�n�c�e� �t�h�a�t� �r�e�q�u�i�r�e�s� �u�n�d�e�r�s�t�a�n�d�i�n�g� �a� �w�i�d�e� �r�a�n�g�e� �o�f� �s�c�i�e�n�t�i�f�i�c� �c�o�n�c�e�p�t�s�,� �t�h�e� �B�C�-‐�E�S�P� �o�f�f�e�r�s� �n�u�m�e�r�o�u�s� �p�o�s�s�i�b�i�l�i�t�i�e�s� �f�o�r� �i�n�t�r�o�d�u�c�i�n�g� �s�t�u�d�e�n�t�s� �t�o� �t�h�e� �n�a�t�u�r�e� �o�f� �s�c�i�e�n�t�i�f�i�c� �i�n�q�u�i�r�y� �a�n�d� �t�o� �a� �w�i�d�e� �r�a�n�g�e� �o�f� �i�m�p�o�r�t�a�n�t� �s�c�i�e�n�t�i�f�i�c� �c�o�n�c�e�p�t�s�.� �S�e�i�s�m�o�g�r�a�p�h�s� �m�e�a�s�u�r�e� �t�h�e� �p�u�l�s�e� �o�f� �t�h�e� �E�a�r�t�h�,� �a�n�d� �p�r�o�v�i�d�e� �d�i�r�e�c�t� �i�n�f�o�r�m�a�t�i�o�n� �a�b�o�u�t� �e�a�r�t�h�q�u�a�k�e


Presenting Author: Anastasia Moulis

31


THE NEW MADRID EARTHQUAKES BICENTENNIAL: A TEACHABLE MOMENT?

NEW MADRID EARTHQUAKE BICENTENNIAL EXECUTIVE COMMITTEE, co-‐chairs: CRAMER, Chris H., CERI, University of Memphis, Memphis, 38152-‐3050, USA, [email protected], and WILKINSON, James M., Central US Earthquake Consortium, Memphis, 38118, USA, [email protected]

Abstract: The bicentennial of the 1811-‐1812 New Madrid sequence of M7 earthquakes is an opportunity for public outreach and education as well as for an advancement of scientific and engineering knowledge. Several agencies and organizations are planning public outreach and education events in addition to scientific and engineering conferences to highlight the New Madrid Bicentennial (NMB). Over the last two years the Central U.S. Earthquake Consortium (CUSEC), the U.S. Geological Survey (USGS), and the Center for Earthquake Research and Information (CERI) at the University of Memphis have been encouraging New Madrid Bicentennial events and participation by the public, governments, universities, and the private sector. Public outreach and education activities include townhall meetings on earthquake hazard, earthquake awareness weeks, community participation in a Great Central U.S. ShakeOut, and production of video presentations on the New Madrid earthquakes. Government agencies involved with emergency management on the local, state, and national levels are involved with earthquake response preparations and a national level exercise through CUSEC and the Federal Emergency Management Agency (FEMA). Scientific and engineering research is encouraged by the USGS via NEHRP grants, by the Earthquake Engineering Research Institute (EERI) via a New Madrid Scenario project involving earthquake effects on participating central U.S. communities, and by the National Science Foundation’s Earthscope USArray project crossing the country. Businesses are being encouraged to prepare for a major New Madrid earthquake through business continuity workshops in addition to public outreach efforts. National scientific and engineering conferences are planned for the SSA annual meeting in Memphis, TN in April 2011, including a public forum, for the Eastern Section SSA annual meeting in Little Rock, AR in October 2011, and for the National Earthquake Conference (NEC) and EERI joint meeting in Memphis, TN in March 2012. Please visit the NMB website at newmadrid2011.org for more information and updates.


Presenting Author: Chris Cramer

32


LINEAR SITE-EFFECT VARIATION FOR HIGHER-FREQUENCY (> 2HZ) GROUND MOTIONS IN SOUTHWESTERN INDIANA, CENTRAL UNITED STATES

PASCHALL,A.M.,Dept. of Earth and Environmental Sciences, University of Kentucky,101 Slone Building,Lexington,KY 40506, [email protected];WOOLERY, E.W.,Dept. of Earth and Environmental Sciences, University of Kentucky,101 Slone Building,Lexington, KY 40506, [email protected]; WANG,Z.,Kentucky Geological Survey,University of Kentucky, 228 MMRB,Lexington, KY 40506,[email protected];SCHAEFER,J.,U.S. Army Corps of Engineers,Louisville District,Louisville, KY 40201, [email protected]; STREET,R.L.,13813 Werth Rd,Hermosa, SD 57702,[email protected]

Abstract: The April 18, 2008 M5.2 Mt. Carmel, Illinois earthquake and its aftershocks (M 4.6, 4.0, and 3.7) triggered strong-‐motion stations along the lower Ohio River and tens of blast monitors in Indiana, Illinois, and Kentucky coalfield region. In this study the observed peak horizontal ground motions in the area of southwestern Indiana were used to constrain empirical estimates and 1-‐D linear approximations of the site effect. An observed amplification factor at each site was determined by comparing the recorded free-‐field motion and current predictive relationships for the eastern and central United States. Dyna�m�i�c� �s�i�t�e� �p�r�o�p�e�r�t�i�e�s� �f�o�r� �t�h�e� �n�o�n�-‐�l�i�t�h�i�f�i�e�d� �s�e�d�i�m�e�n�t�s� �a�n�d� �b�e�d�r�o�c�k� �w�e�r�e� �m�e�a�s�u�r�e�d� �u�s�i�n�g� �s�h�e�a�r�-‐�w�a�v�e� �(�S�H�)� �r�e�f�r�a�c�t�i�o�n�/�r�e�f�l�e�c�t�i�o�n� �s�u�r�v�e�y�s�.� �A�l�t�h�o�u�g�h� �1�-‐�D� �t�r�a�n�s�f�e�r� �f�u�n�c�t�i�o�n� �c�a�l�c�u�l�a�t�i�o�n�s� �d�i�d� �n�o�t� �u�n�i�v�e�r�s�a�l�l�y� �c�o�r�r�e�l�a�t�e� �w�i�t�h� �t�h�e� �o�b�s�e�r�v�a�t�i�o�n�s�,� �r�e�s�u�l�t�s� �i�n�d�i�c�a�t�e� �t�h�a�t� �t�h�e�y� �b�e�t�t�e�r� �a�p�p�r�o�x�i�m�a�t�e�d� �t�h�e� �r�e�c�o�r�d�e�d� �o�b�s�e�r�v�a�t�i�o�n�s� �t�h�a�n� �t�h�e� �e�m�p�i�r�i�c�a�l� �c�o�e�f�f�i�c�i�e�n�t�s�.� �S�o�u�r�c�e�s� �o�f� �t�h�e� �v�a�r�i


Presenting Author: Anthony Paschall

33


THE SOUTHERN APPALACHIANS: COMPLEX LITHOSPHERIC STRUCTURE ASSOCIATED WITH MULTIPLE WILSON CYCLES

POWELL, Christine, Center for Earthquake Research and Information, University of Memphis, Memphis, TN 38152; VLAHOVIC, Gordana, ARROUCAU, Pierre, Department of Environmental, Earth and Geospatial Sciences, North Carolina Central University, Durham, NC 27701; CHAPMAN, Martin, Department of Geosciences, Virginia Tech, Blacksburg, VA 24061

Abstract: The Southern Appalachians record a rich tectonic history covering two complete Wilson cycles. Of particular interest is the convergence of the granite-‐rhyolite, Grenville, Ouachita, Appalachian, and Mesozoic-‐Tertiary lithospheres. This zone of convergence is obvious on the magnetic map of North America and contains a wealth of information concerning the construction of the North American continent. The region covering parts of Alabama, Georgia, and North and South Carolina has experienced multiple continental convergences, suturing, and rifting episodes. Of equal interest is the origin of another obvious feature on the magnetic map, the New York – Alabama (NY-‐AL) magnetic lineament. The magnetic gradient defining the NY-‐AL is particularly well defined in eastern Tennessee where it appears to control the trend of the active eastern Tennessee seismic zone (ETSZ). The high rate of spatially concentrated earthquake occurrence in the ETSZ, compared to most of the rest of the eastern United States, will offer a unique opportunity for resolving lithospheric structure, and should make the ETSZ a high priority target. Detailed, 3D Vp and Vs models for the upper and middle crust already exist for the ETSZ. Joint inversions of magnetic and gravity fields are providing further insight into the origin of the NY-‐AL magnetic anomaly and other potential field anomalies associated with basement features. We suggest that the passage of the EarthScope Transportable Array coupled with FlexArray deployments will provide the regional array capability to properly interpret the complex basement features illustrated in the magnetic anomaly map and investigate deeper lithospheric structure associated with the edge of the continent.


Presenting Author: Christine Powell

34


NEW EARTHQUAKE RELOCATIONS FOR THE NEW MADRID SEISMIC ZONE

POWELL, Christine, DESHON, Heather, Center for Earthquake Research and Information, University of Memphis, Memphis, TN, 38152

Abstract: Earthquakes in the Cooperative New Madrid Seismic Network catalog for the period 1996-‐2008 are relocated using 3D Vp and Vs models determined using the inversion method tomoFDD. The dataset contains the most accurate New Madrid seismic zone (NMSZ) earthquake locations to date and delineates interesting fault complexity associated with the four major arms of NMSZ seismicity. The major arms include two NE trending, right-‐lateral strike-‐slip faults (the Cottonwood Grove – Blytheville Arch (CGBA) fault and the northern arm) offset by a NW trending reverse fault (Reelfoot fault (RF)). A fourth arm trends EW from the northern termination of the RF. The simple structural model of two strike-‐slip faults offset by a left-‐stepping reverse fault is complicated by the extension of the RF south of its intersection with the CGBA and by the presence of the EW trending arm. Our relocations reveal distinct differences between the northern portion of the RF (north of the CGBA) and the southern portion. In the northern portion, earthquakes occur in distinct clusters that delineate a SW dipping fault plane extending from about 6 to 14 km depth. Two distinct, parallel clusters of earthquakes are often observed indicating the presence of parallel fault planes. Northern RF seismicity is associated with low Vp/Vs ratios produced by low Vp and high Vs anomalies. The earthquakes de-‐cluster markedly at the probable intersection of the CGBA with the RF. South of the intersection, seismicity defining the RF becomes shallower and more dispersed. This portion of the southern RF is associated with swarm activity and low Vp and Vs anomalies. The northern arm of seismicity consists of two parallel, near-‐vertical faults. Earthquake relocations and associated velocity anomalies are discussed in the context of a seismotectonic model for the NMSZ.


Presenting Author: Christine Powell

35


SEISMOLOGY AT SUNY POTSDAM, NY

REVETTA, Frank A., VALENTI, Peter V., Department o

delineating)paleoseismologicalfeatures...

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