Inversion of near-field waveform data for earthquake source rupture process ( II ): Inversion of Chi Chi earthquake source, 20 September, 1999, Taiwan |
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Authors: | Zhou Shiyong and Chen Xiaofei |
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Institution: | (1) Department of Geophysics, Peking University, Beijing, 100871, China |
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Abstract: | The new inversion algorithm developed based on the recent progress in the nonlinear programming study by us is used to invert
the earthquake source process of Chi Chi earthquake M
w7.6, 20 Semptember, 1999, Taiwan. A curve fault model is constructed in our inversion to make the fault model close to the
real rupturing fault to reduce the influence from the discrepancy between the constructed fault model and the real rupturing
fault. The results show that (1) the rupture process of the Chi Chi earthquake source lasted about 32 seconds and the main
faulting occurred between 6th to 21st second after the start of the ruptures and the high slip area were mainly located at
the northern segment of the fault. (2) The slip was dominated by thrust faulting. The average rake angle was 64.5°, which
was very consistent with those inverted by USGS, Harvard and CWB (Central Weather Bureau of Taiwan). The amount of the moment
inverted in this paper was 7.76×1020 NM, which was a slightly bigger than those inverted by USGS and Harvard. (3) A clear nucleation step existed in the source
faulting process and it lasted about 6 seconds. The moment release rate accelerated obviously at the end of the nucleation
step. The faulting started from the southern segment and mainly occurred at the northern segment after 10 seconds. At the
end of this paper, we analyzed the reliability of the inversion result via comparing with the GPS observations and discussed
its scientific signification. |
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Keywords: | Chi Chi earthquake source rupture process waveform inversion near-source data source mechanism |
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