Earthquake simulations in the Salt Lake Basin for the validation of the Wasatch CVM: long period (T>1.0-s) seismic response (original) (raw)

2010

Abstract

The Wasatch Fault bounds the Salt Lake Basin (SLB), Utah to the east and is capable of producing M7 earthquakes. In order to characterize the seismic hazard that such earthquakes pose to Salt Lake City and other heavily populated regions along the Wasatch Front, we require estimates of potential earthquake ground motions. However, the long recurrence time of these events (~1.3ky) necessitates that these estimates be derived from empirical relations observed in other regions or from deterministic modeling. Although previous and on-going studies (Liu et al., 2010; Roten et al., 2010) have begun to examine the earthquake ground motions caused by simulated M7 events on the Salt Lake Segment of the Wasatch Fault, a comprehensive validation of the Wasatch Community Velocity Model (WCVM) (Magistrale et al., 2006) has not yet been performed. We present the results from systematic testing of the intrinsic attenuation and seismic wave speed relations in the WCVM. Modifications to the empirical wavespeed relations and selection of intrinsic attenuation relations for the WCVM version 3c are made to minimize the differences between simulated and observed seismograms from small (M<5) earthquakes in the Wasatch Front. Simulations are carried out with the Hercules finite element tool-chain (Tu et al., 2006) and are valid at frequencies up to 1 Hz. We find a good agreement between body wave arrival times from the observed and simulated events. Discrepancies in the peak ground velocities and waveform durations are reduced in the final model. Some unresolved differences in the observed and synthetic seismograms persist and may result from un-modeled heterogeneities outside of the Salt Lake Basin. Future modeling efforts in the Wasatch Front may apply these results for improved earthquake ground motion estimates.

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