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William Schermerhorn Thesis Proposal

October 28 @ 3:00 pm - 5:00 pm MDT

William Schermerhorn

A Tale of Two Cities: Las Vegas, NV and Charleston, SC Earthquake Hazard Characterization

The determination of in-situ shear-wave velocity (Vs) and active fault characterization are critical parameters needed to assess earthquake hazards. Using active source seismic approaches, I investigate the influence of local site conditions within the epicentral zone of the 1886 Charleston, South Carolina earthquake, and in Las Vegas, Nevada, characterize and produce the first cross-section images of several active faults.

While the identification of faults related to the destructive 1886 Charleston M 6.9-7.3 earthquake have eluded scientists for over a century, several studies have indicated that ground shaking damage in Charleston may be enhanced by local soil conditions, such as low Vs unconsolidated Quaternary deposits. These deposits can both amplify earthquake ground motions and can generate liquefaction. Using new seismic data collected within the 1886 epicentral region, I determine that high frequency site response is primarily driven by the thickness of low Vs Quaternary deposits. Coupled with the proximity to active faults that I identify within the 1886 epicentral area, thick deposits of low Vs soils promote localized ground shaking and amplify ground motions.

Las Vegas Metropolitan area resides in a basin that is traversed and bounded by numerous active faults. Despite this knowledge, the seismic potential related to the Las Vegas Valley Fault System (LVVFS) and Frenchmen Mountain fault (FMF) remain largely unresolved. The Eglington fault is considered to be a major controlling source in current earthquake simulations for the LVVFS. The FMF, a major range-front normal fault bounding the eastern margin of the basin, is considered 100% tectonic. While recent and past FMF excavations have documented evidence for multiple earthquake-related displacements, the structural relationship between individual faults is unresolved. Additionally, slip rate estimates are highly variable, and to date, earthquake recurrence rates are poorly constrained. 6 km of optimally located seismic transects that cross the LVVFS and FMF are planned for November 2020. Seismic reflection images from these transects will allow for characterization of slip rates, determination of the kinematic and geometric relationship between distinct fault splays, and will provide constraints needed to improve recurrence interval estimates.

Advisor: Lee Liberty

Co-Advisors: Dylan Mikesell, Brittany Brand

When: October 28, 2020
Time: 3:00 PM
Where: Zoom Meeting ID: 973 0089 6586