HR: 16:15h
AN: S54A-02    [Abstracts]
TI: Importance of covariance components of waveform data with high sampling rate in seismic source inversion
AU: * Yagi, Y
EM: yagi-y@geol.tsukuba.ac.jp
AF: University of Tsukuba, 1-1-1 Tne'nodai, Tsukuba, 305-8572, Japan
AU: Fukahata, Y
EM: fukahata@eps.s.u-tokyo.ac.jp
AF: University of Tokyo, 7-3-1 Hongo, Bunkyoku, Tokyo, 113-0033, Japan
AB: As computer technology advanced, it has become possible to observe seismic wave with a higher sampling rate and perform inversion for a larger data set. In general, to obtain a finer image of seismic source processes, waveform data with a higher sampling rate are needed. Then we encounter a problem whether there is no limitation of sampling rate in waveform inversion. In traditional seismic source inversion, covariance components of sampled waveform data have commonly been neglected. In fact, however, observed waveform data are not completely independent of each other at least in time domain, because they are always affected by un-elastic attenuation in the propagation of seismic waves through the Earth. In this study, we have developed a method of seismic source inversion to take the data covariance into account, and applied it to teleseismic P-wave data of the 2003 Boumerdes �E#202;Zemmouri, Algeria earthquake. From a comparison of final slip distributions inverted by the new formulation and the traditional formulation, we found that the effect of covariance components is crucial for a data set of higher sampling rates (≥ 5 Hz). For higher sampling rates, the slip distributions by the new formulation look stable, whereas the slip distributions by the traditional formulation tend to concentrate into small patches due to overestimation of the information from observed data. Our result indicates that the un-elastic effect of the Earth gives a limitation to the resolution of inverted seismic source models. It has been pointed out that seismic source models obtained from waveform data analyses are quite different from one another. One possible reason for the discrepancy is the neglect of covariance components. The new formulation must be useful to obtain a standard seismic source model.
DE: 7200 SEISMOLOGY
DE: 7203 Body waves
DE: 7260 Theory
SC: Seismology [S]
MN: 2007 Fall Meeting