Simulation of Seismic-Wave PropagationThrough the Lake Tahoe Basin,

Calif.-Nevada: A Scenario Approach toProbabilistic Shaking Hazard

Gretchen C. Schmauder1,2, John N. Louie1,3,Satish Pullammanappallil2, Kyle Gray1, Kevin McBean1,

Alexa McBean1, & Graham M. Kent1

1. Nevada Seismological Lab. & Dept. Geol. Sci. & Engin., Univ. of Nevada, Reno NV, USA2. Optim SDS, 200 S. Virginia St. Suite 560, Reno, NV USA; gretchens@optimsds.com

3. visiting Victoria University of Wellington to August 2014

Thanks to: J. M. Maloney (Univ. of Calif.

San Diego); Edgetech; Watershed Sciences; Tahoe Regional Planning Agency;

U.S. Forest Service

crack.seismo.unr.edu/NSZ

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1) FindingEarthquake Source Faults:Marine CHIRP under Lake TahoeDense LiDAR under trees

LV

LA

SF

Results:Only 3 faults!

(Pyramid L. has 100s)All normal, N-

strike, E-dip, E-W extension

M7.5 events in record

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CHIRP images sediments to 70 m below lake bottom with 25 cm resolution

Edgetech acousticCompressed HighIntensity RadarPulse (CHIRP)

With Univ. of California,San Diego

Slide/gravity deposits seen throughout Tahoe; dated & correlated by Shane Smith.

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Watershed Sciences airborne Light Detection and Ranging (LiDAR) imagery over 232,000 acres in the Tahoe basin

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2) Gravity and ReMi™ Assess Wave Trappingin Basins, and Geotechnical Amplification

AssembledBasinThickness

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AssembledVs30

200-mGrid Vs

AssembledVs30 Map

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Intense 3Dbasin effects

NSZ WTDPFRupture

from South

Large motions for: Steep slopes Small subbasins

3) Shake- Zoning

Scenario Predictions

Using Physics and

GeologyPGVShaking

Map

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How to explain hazard to the community?4) Probabilistic Mapping with ShakeZoning Scenarios

Frankel et al. USGS Seattle Basin – Annual Probability of Exceedance λ:

Sum up a limited number of scenarios: faults; rupture directivities. Examine Annual Rate of Exceedance (A.R.E.) of μ0=30 cm/s. Conflate PGV > 30 cm/s with higher A.R.E.; <30 cm/s, lower A.R.E.

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Shaking Map to Hazard Map

PGVShaking

Map

7x10-5/year

PGV rate

PGV rate A.R.E.Map

WTDPFSo. Rupture, One Scenario

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Now add up the A.R.E.s for the 6 fault scenarios:Result: a simple tool promoting resilience