Three-dimensional simulations of earthquakes have given a deeper understanding of wave propagation and site effects in urban regions. In this work we study the impact of a potential major earthquake on the San Andreas Fault with significant seismic hazard in the Greater Los Angeles Basin. We present results for the ShakeOut simulation---a rupture beginning near Salton Sea, California, heading 270 km northwest along the fault, that produces a Mw 7.8 earthquake in a geographical region which includes all major populated areas of Southern California and northern Mexico, in a 600 km by 300 km by 80 km volume, for a maximum frequency of 1.0 Hz and a minimum shear wave velocity of 200 m/s. For the material model, we use a discretized version of SCEC's CVM4 velocity model, called CVM-Etree. The simulation was performed at the Pittsburgh Supercomputing Center using Hercules, a finite element octree-based, parallel software developed by the Quake Group at Carnegie Mellon University. Hercules implements a highly efficient end-to-end algorithm for solving the wave field in highly heterogeneous media due to kinematic faulting. We verify our results by comparing synthetic seismograms computed with a parallel finite difference code by Robert Graves (URS) for a similar scenario earthquake, for a maximum frequency of 0.5 Hz and minimum shear wave velocity of 500 m/s. We focus our analysis of the results of the 1.0 Hz ShakeOut simulation on the Los Angeles Basin area, and the Santa Clara River Valley and Oxnard Plain. We examine the site effects present in these two areas and their proneness to capture and amplify seismic waves due to their geological features. Results show a direct correlation between the amplification levels and the local soil and basin profiles.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 1706 Computational geophysics;
- 7212 Earthquake ground motions and engineering seismology;
- 7290 Computational seismology