Wave equation dispersion inversion of surface waves recorded on irregular topography

Abstract

Significant topographic variations can strongly influence the amplitudes and phases of propagating surface waves. Such effects should be taken into account, otherwise the S-velocity model inverted from the Rayleigh or Love dispersion curves will contain significant inaccuracies. Here, we show that the recently developed wave equation dispersion inversion (WD) method naturally takes into account the effects of topography to give accurate S-velocity tomograms. Application of topographic WD (TWD) to synthetic data demonstrates that TWD can accurately invert for the S-velocity model from dispersion curves computed from data recorded over variable topography. This method is applied to ambient noise seismic field data recorded along the Clark strand of the San Jacinto fault zone in Southern California. The resulting TWD S-velocity tomogram appears to be more consistent with the geology than the standard WD tomogram.