Finite Source Parameters Using Strong Motion Waveforms of Taiwan TSMIP Data: A Case Study of 22 October 1999 Chiayi, Taiwan, Earthquake

Abstract:

Inverting seismic waveforms for the finite fault source parameters of earthquakes is important for reconstruction of faulting processes including both the properties of the fault and transient stress field. It is also significant to image seismogenic structures in urban areas. Here we analyze the finite-source process and test for the causative fault plane using the accelerograms recorded by the Taiwan Strong-Motion Instrumentation Program (TSMIP) stations. The point source parameters for more than 100 Mw>4 earthquakes were first obtained by complete waveform moment tensor inversions. Then we use part of this catalog to study the 22 October 1999 (Mw 5.6) earthquake sequence near the city of Chiayi, Taiwan, where a damaging earthquake occurred a century ago. We have derived the change in the duration of the apparent source time functions (ASTFs) using a new Empirical Green Function Deconvolution method to estimate the mainshock rupture propagation processes. Preliminary results show the mainshock ruptured on the NNE-SSW trending right-lateral strike-slip fault and propagated toward SSW direction. To further characterize the faulting, we are using a finite fault inversion code developed by Dreger and Kaverina (2000) to derive a slip distribution model of this mainshock. The procedure developed from this study can be applied to other strong motion events to better understand their kinematic source parameters.