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Ground-Motion Simulation and Validation of the 2008 Chino Hills, California, Earthquake

Ricardo Taborda, & Jacobo Bielak

Published February 2013, SCEC Contribution #1520

We present a simulation of the Mw 5.4 2008 Chino Hills earthquake for a maximum frequency up to 4 Hz and a minimum shear-wave velocity down to 200 m/s and perform a validation study comparing data obtained from seismic networks with simulation synthetics on more than 300 recording stations. The simulation was done using a parallel-computing code for earthquake simulations that implements a finite-element solution to anelastic wave propagation in heterogeneous media. The source model corresponds to that of an independent inversion study, and the material model used is a Community Velocity Model (CVM) developed by the Southern California Earthquake Center. Our results for the goodness-of-fit measure of the synthetics indicate that, from a regional perspective, the simulation starts to deviate from the data at frequencies above 1 and 2 Hz. At particular locations or station clusters, however, the synthetics yield very good results, even at frequencies between 2 and 4 Hz. The best results are obtained between 0.1 and 0.25 Hz over the entire region, and up to 1 Hz within the major basins. These and other results from comparisons at boreholes, biases of the peak surface response, and the differences in the strong-phase duration of the waveforms and the arrival time of $P$ waves suggest a strong sensitivity to seismic velocities. In particular, the CVM used seems to misrepresent the shallow soil deposits and over-estimate seismic velocities in the upper layers outside the basins. These observations are helpful in identifying regions where the velocity model may need to be revised. Overall, this study shows that extending the maximum frequency for deterministic earthquake simulations beyond 1 Hz is an effort worth pursuing.

Taborda, R., & Bielak, J. (2013). Ground-Motion Simulation and Validation of the 2008 Chino Hills, California, Earthquake. Bulletin of the Seismological Society of America, 103(1), 131-156. doi: 10.1785/0120110325.