Assessing site effects by full waveform modeling

Leo Eisner, & Robert W. Clayton

Under Review 2001, SCEC Contribution #558

We have developed methodology to evaluate theoretical site effects in a complex heterogeneous media using synthetic Green functions. The Green functions are calculated numerically by inserting body forces at the site of interest and then recording the reciprocal Green functions along an arbitrary finite fault surface. Using synthetic Green functions we can simulate arbitrary source scenario. This methodology does not require empirical attenuation curves derived from previously observed data (which may not be representative for the selected site) or regressing characteristic parameters of synthetic seismograms over arbitrary selected basin parameters.

With an accurate velocity model we may replace the long period part of the attenuation curves with a site specific but more accurate theoretical site effects. Using the Southern California velocity model we have evaluated the theoretical site effects for three sites in the vicinity of the Los Angeles basin. The new methodology allowed us to simulate 15 realistic source scenarios for 5 major Southern California faults and compare their response in the selected sites. In agreement with previous studies (Olsen 96, Graves 98) we have found the largest amplitudes can be observed from the earthquakes on local faults rather than an earthquake on the San Andreas fault.

Citation
Eisner, L., & Clayton, R. W. (2001). Assessing site effects by full waveform modeling. Bulletin of the Seismological Society of America, (under review).