Evaluating Late Pleistocene and Holocene Rupture, Seismic Hazards and Ground Motion in the Lake Tahoe Basin
AuthorSchmauder, Gretchen Cathleen
Geological Sciences and Engineering
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Chapter two in this study is a reevaluation of active faulting across the Tahoe basin a combination of airborne LiDAR (Light Detection and Ranging) imagery, high-resolution seismic CHIRP profiles, multibeam bathymetric mapping, and field mapping. The combined lateral and vertical resolution has allowed a straight forward identification of the landward extension of fault scarps associated with the three major active fault zones in the Tahoe basin: the West Tahoe-Dollar Point fault, Stateline-North Tahoe fault, and Incline Village fault. Chapter 3 in this study evaluates seismic hazard within the basin as a result of earthquake rupture on the faults identified in the first part of this study. The Ground motions modeled using Nevada ShakeZoning, a physics-based method incorporating geotechnical information and basin shape determined from geophysical methods, peak ground velocity (PGV) maps considerably different (and more accurate) than those obtained from ShakeMap, a standard USGS tool for ground motion estimation. Although ShakeMap over-predicts ground shaking outside the Lake Tahoe basin, it substantially under-predicts ground motions within the basin. eWave propagation models indicate strong, sustained shaking in the basin, threatening several communities. Annual rates of exceedance maps show the higher rates of exceedance of key ground-motion levels strongly correlate with the basin shape. The purpose of this study is to provide both better ground motion estimates and more useful shaking maps to local communities. Chapter 4 begins the validation process of the models developed as part of Chapter 3 to events recorded at Nevada Seismological Laboratory seismic stations.