CyberShake PSHA with Updated Rupture Models

Session: Numerical Modeling of Rupture Dynamics, Earthquake Ground Motion and Seismic Noise
Type: Oral
Date: 4/29/2020
Time: 02:45 PM
Room: 230 + 235
Description: 

The Southern California Earthquake Center (SCEC) has developed CyberShake to produce 3D physics-based probabilistic seismic hazard analysis (PSHA) models using deterministic wave propagation simulations and a reciprocity-based approach. To date, CyberShake has been used to calculate over a billion seismograms for over 1600 sites in California, resulting in hazard maps for the Los Angeles region, Central California and the San Francisco Bay Area. We find that CyberShake produces larger basin amplification effects at long periods (>2 sec) than GMPEs for basins such as the Los Angeles and San Joaquin, likely due to complex 3D velocity structures which are difficult to capture in a typical GMPE parameterization.

One key step in the CyberShake software platform is converting rupture descriptions and magnitude from the earthquake rupture forecast (ERF; typically UCERF2) into the full slip time histories required for simulation. We have recently integrated the latest version of the Graves-Pitarka rupture generator into the CyberShake workflows, which includes increased variability in rupture parameters and decreased coherency (Graves & Pitarka 2019). We will present CyberShake PSHA results with this new generator for a variety of sites, showing the impact of the new rupture generator on simulated ground motion and hazard.

To sample rupture variability and capture directivity effects, the CyberShake rupture generator samples hypocenters along the fault surface. We have investigated the effect of varying the density of hypocentral spacing on hazard. We have performed a sensitivity analysis of this parameter using CyberShake simulations, and will present our results showing the impact of increased hypocentral spacing density on overall hazard.

Presenting Author: Scott Callaghan

Authors