gph 492/692 spring break field project overview &...

L. Travis West University of Nevada, Reno

GPH 492/692 Spring Break

Field Project Overview & Reno Project Proposal

3-19-16 to 3-27-16


Field Areas➢1.) Seven Lakes, CA

➢NW of Reno ➢2 days

➢ proposal (Steve Angster)

➢2.) Reno, NV ➢proposal (LTW)

NVCA


Methods➢Reflection -> 7 Lakes ➢Refraction -> 7 Lakes ➢Electrical Resistivity -> 7 Lakes ➢Magnetics -> 7 Lakes ➢Deep ReMi -> Reno ➢ReMi “shallow” 48ch L-array -> Reno ➢Gravity -> Reno ➢H/V -> Reno ➢GPS


7 Lakes area

possible reflection/refraction line

➢OBJ: Characterize and locate fault related structure

➢Methods used: ➢Reflection ➢Refraction ➢Magnetics ➢Resistivity

Field Area: Seven Lakes, CA

NVCA


Field Area: Reno, NVReno area

➢OBJ: Build upon existing database for seismic hazard

➢Methods used: ➢Deep ReMi ➢ReMi “shallow” ➢H/V ➢Gravity ➢GPS

Mount Rose fault zone

L. Travis West University of Nevada, Reno modified form Wesnousky (2005)

Regional Tectonic Setting➢The Walker Lane,

ECSZ, and B&R takes up approximately 25%, of associated R-L slip plate motion


EQ hazard significant for Reno Area

modified form dePolo (1999) http://geohazards.usgs.gov/eqprob/2009/output/7598.pdf)


EQ Modeling

modified form dePolo (1999)

Soils are assumed to besofter (yellow to green)in basins, harder (blue)in bedrock.

P06A

SSFS

PEA

RFNVNOAA

SF02

SPHIRF08 RENOSMRN

NMHSUNRN

MOGLRFMA LOVE

UNRX SWTPHUMA

RNO1RF05

WGLFCRWR

WYRD HVGCSKYF

PICO

BMHS

10 miles

SpanishSprings

Sparks

Verdi Reno

SouthMeadows

Soil Strength MapMogul Magnitude 5.0 Scenario

Basin Model 2

Softest soils arein eastern valley,will amplifyshaking.

P06A

SSFS

PEA

RFNVNOAA

SF02

SPHIRF08 RENOSMRN

NMHSUNRN

MOGLRFMA LOVE

UNRX SWTPHUMA

RNO1RF05

WGLFCRWR

WYRD HVGCSKYF

PICO

BMHS

10 miles

SpanishSprings

Sparks

Verdi Reno

SouthMeadows

Computed Maximum ShakingMogul Magnitude 5.0 Scenario

Basin Model 3: Widmer et al., 2007

Additional basindetails near Mogulyield a more complexPGV map. (Yellowat 5 cm/s.)

Basins amplifyground motion,but in complexpatterns.

➢Reno-Area Geotechnical Model and M5 Scenario

Louie, 2009


Existing Geophysical Coverage: Reno ➢Deep ReMi

➢2012,2014,2015 ➢H/V, 2015 ➢ReMi Vs30

➢2004, 2007, 2008 ➢gravity, 2000 ➢Reflection, 2009

INCOMPLETE!


Basin depth

Depth to Bedrock in Reno and Carson City 345

alluvium-bedrock density contrast of −0.33 g/cm3. A constantaverage density contrast of −0.33 g/cm3 produced results mostconsistent with previous well and seismic data for both Renoand Carson City. There is evidence that the residual gravityseparation may not have completely succeeded near this sub-basin. Figure 4, the bedrock gravity grid, also shows a gravitylow over this area. Note that the infinite slab approximation un-derestimates basin depth for a given density contrast. Becausewe used well-log information to calibrate depth at certain areas,the density contrast required in the infinite slab approximationwas underestimated to compensate. Sediment density is likelyto be less than the 2.34 g/cm3 we used.

The westernmost elongation of the basin represents the east-west trending Tertiary Verdi basin. This basin is underlain bythe Miocene-Pliocene Hunter Creek sandstone formation. Thesandstone has a lower average density than the alluvium ofthe Truckee Meadows. As such, the depth of the basin maybe slightly shallower than indicated on the depth-to-bedrockmaps (Figures 6 and 7). A subbasin in the Steamboat Springsarea is represented by another gravity low to the southwest,with −6 mGal local anomaly, corresponding to a depth of ap-proximately 430 m.

The east-west cross-section along the Truckee River in Reno(Figure 8) yields a maximum basin depth of 1000 m. This profileshows a striking structural trough in the western portion of thebasin. The maximum basin depth in this model is under WestMcCarran Boulevard. A second trough in the eastern portion

FIG. 7. Depth-to-bedrock in Reno–Truckee Meadows as computed with the infinite slab approximation, assuming average basindensity contrast of −0.33 g/cm3. Geologic units are as in Figure 2. Depths are in meters, contour interval is 200 m; new measuringstations are triangles, existing coverage are white circles. Wells with logged Kate Peak andesite bedrock depths show white numbersin black circles. Logged wells that did not reach bedrock show their total depth in black numbers with a “>” (greater than) in whitecircles. Wells without logs have their total depths in black numbers with “≥” (greater than or equal to) symbol, also in white circles.Numbers outside circles refer to the list in Table 1. Major roads are labeled.

of the basin is separated from the western trough by a bedrockridge that comes within 200 m of the basin surface near theReno/Tahoe International Airport.

The anomaly maps of Carson City (Figures 9–11) showan elongate north-south gravity low over Eagle Valley. Theanomaly closely approximates the anomaly shape of Arteaga(1986), which he mapped using a combination of gravityand seismic techniques. The magnitude of the local anomaly,−7 mGal, is much smaller than in the Truckee Meadows, sug-gesting a shallower basin depth. This corresponds to a 520-mdepth with the infinite slab approximation (Figure 12, assum-ing a −0.33 g/cm3 density contrast). The northeast-trendingcontours in the northern part of the basin are poorly con-strained and may be an artifact of the poor data coverage in thearea. A subbasin to the northwest is separated from the mainbasin by the subsurface expression of a northwest-southeasttrending ridge of Triassic metavolcanic rocks. This formationoutcrops at Lone Mountain in northern Carson City (Trexler,1977).

An east-west cross-section along 5th Street in Carson City(Figure 13) yields a maximum basin depth of 530 m. The 5thStreet transect shows Eagle Valley to be a more symmetricalbasin in which the depth increases fairly smoothly to 0.53 kmbefore returning to bedrock on either side of the basin. Thedensity scheme used is from Table 2. The maximum basin depthalong this transect is located 1.5 km east of US Highway 395(Figure 13).

modified form Abbott & Louie (2000)

➢Gravity is ill-defined Eastern and Southeastern Basin Margin


Team Responsibility ➢Pre-Deployment:

➢Research relevant data for study area ➢Devise plan of attack with Grad faculty

➢Deployment: ➢Training of other teams on your method ➢Data quality assurance

➢Post deployment: ➢Data processing and interpretation ➢Present results ➢Data archiving


Data Collection Procedure➢Everybody participates ➢Each team does every method ➢Split up into 1/2 days:

➢minimum 2 teams on one method ➢one team training the next then rotate out

➢Some methods may require multiple teams: ➢Deep Remi ➢Reflection/refraction


Final Project Questions➢what is the current coverage for your method and

relevant data? If any? ➢How well does your data tie into the existing

➢does it make sense? ➢ground truth

➢How does your data meet the project obj? ➢Does it improve the model?

➢ is there a anomaly? ➢ improve poorly constrained coverage

➢Can you identify geologic structure ➢ i.e. broken reflectors, velocity discontinuities


Research Resources ➢http://earthquake.usgs.gov/research/

external/research.php ➢http://research.utep.edu/Default.aspx?

alias=research.utep.edu/paces ➢http://crack.seismo.unr.edu/ftp/pub/louie/

class/492/field03/ ➢http://crack.seismo.unr.edu/ftp/pub/louie/

class/453/faultsurvey/presentations/ ➢http://crack.seismo.unr.edu/wbrcvm/


Literary Review: Reno➢W. J. Stephenson, R. N. Frary*, J. N. Louie, and J. K. Odum, 2013, Quaternary

extensional growth folding beneath Reno, Nevada, imaged by urban seismic profiling: Bulletin of the Seismological Society of America, 103, no. 5 (October), doi: 10.1785/0120120311, 2921-2927. (8.9 Mb PDF journal proof)

➢A. Pancha*, J. G. Anderson, J. Louie, and S. Pullammanappallil, 2008, Measurement of shallow shear wave velocities at a rock site using the ReMi technique: Soil Dynamics and Earthquake Engineering, 28, 522-535.

➢ Aasha Pancha, John G. Anderson, and John N. Louie, 2007, Characterization of near-surface geology at strong-motion stations in the vicinity of Reno, Nevada: Bulletin of the Seismological Society of America, 97, 2096-2117.

➢J. B. Scott*, M. Clark*, T. Rennie, A. Pancha*, H. Park* and J. N. Louie, 2004, A shallow shear-wave velocity transect across the Reno, Nevada area basin: Bulletin of the Seismological Society of America, 94, no. 6 (Dec.), 2222-2228. ( 2.8 Mb PDF)

➢ I. M. Tibuleac, D. H. von Seggern, J. N. Louie and J. G. Anderson, 2009, High resolution seismic velocity structure in the Reno basin from ambient noise recorded by a variety of seismic instruments: presented at the 2009 Geothermal Resources Council Annual Meeting, Reno, Nevada, Oct. 6.http://www.seismo.unr.edu/geothermal/TibuleacGRC2009_poster_noise.png

http://www.seismo.unr.edu/geothermal/TibuleacGRC2009_poster_noise.png


➢John N. Louie, 2001, Faster, better: shear-wave velocity to 100 meters depth from refraction microtremor arrays: Bulletin of the Seismological Society of America, 91, no. 2 (April), 347-364.

➢Robert E. Abbott* and John N. Louie, 2000, Depth to bedrock using gravimetry in the Reno and Carson City, Nevada area basins: Geophysics, 65, 340-350. ( 24 Mb high-resolution PDF)

➢Master of Science Thesis in Hydrogeology by Matthew Clark on ``Hydrologic and geophysical investigation of a fault as a hydrologic barrier in Reno, Nevada'' defended Oct. 26, 2005 and finalized Dec. 2008.

➢Pancha A., 2012, Determination of 3D-Velocity structure across the Deepest Portion of Reno area BasinG12AP20026

➢PanchaA., 2014, Determination of 3D-Velocity structure across teh Northeast Reno arae Basin FTR-G14AP00020

➢Nakamura, Y., 1989, A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface. Quarterly Report of Railway Technical Research, 30, 25-33

➢Widmer (2005) Gravity-based geological modeling of the central truckee meadows, preepared for teh Central truckee Meadows Remediation District, Washoe County Department of Water resourecs

Literary Review: Reno


➢Wesnousky, 2005, The San Andreas and Walker Lane fault systems, western North America: Transpression, transtension, cumulative slip and the structural evolution of a major transform plate boundary, Journal of Structural Geology, 27, 1505-1512

➢Robert E. Abbott* and John N. Louie, 2000, Depth to bedrock using gravimetry in the Reno and Carson City, Nevada area basins: Geophysics, 65, 340-350. ( 24 Mb high-resolution PDF)

➢http://geohazards.usgs.gov/eqprob/2009/output/7598.pdf)

➢DePolo, 1999, Earthquakes in Nevada, 1852-1998, Nevada Bureau of Mines and Geology, map- 19.

➢Louie, 2009, Gathering criitical data towards the Western Basin Range CVM, Poster at 2009 SCEC annual meeting, http://crack.seismo.unr.edu/ftp/pub/louie/talks/Louie-SCEC09poster.jpg

References

http://crack.seismo.unr.edu/ftp/pub/louie/talks/Louie-SCEC09poster.jpg

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