HR: 1330h
AN: S32A-0843    [PDF]
TI: Refining the Southern California 3D Model in the \\Los Angeles Area Using Seismic Waveforms
AU: * CHU, R
AU: ZHU, L
AB: \hspace{8 mm}A standard three-dimensional (3D) reference model is under development by the southern California Earthquake Center (SCEC) to provide realistic seismic velocity models for better simulation of ground motion from damaging earthquakes, path and site effects, and for precise location of earthquake source. In this model, P velocities of major southern California sedimentary basins (Los Angeles basin, Ventura basin, San Gabriel Valley, San Fernando Valley, Chino basin, San Bernardino Valley, and the Salton Trough) are determined from maximum burial depth and age of the sediments following certain empirical rules. S velocity and density are then derived from the P velocity. Because the velocities are indirectly determined and there are large uncertainties in those empirical rules and the input geologic parameters, it is necessary to validate and refine the 3D model using observed seismic records. In this study, we computed teleseismic receiver functions of southern California basin stations using an iterative time-domain deconvolution. P-to-S conversions from the bottom of basins were clearly identified. Their amplitudes and delays with respect to the direct P wave vary strongly with incident directions, which are presumed caused by basin geometry. We used a 4th-order 3-D finite-difference code to compute synthetic receiver functions to compare with observations. Parameters to be determined by the forward modeling include shape of the base and velocity contrast. The results will provide an independent verification and, most likely, improvement of the SCEC 3D model in the metropolitan Los Angeles region.
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting