A new inversion algorithm for simultaneously reconstructing the slip vectors and rupture times of a propagating finite fault is developed based on the recent progress in the nonlinear pro-gramming study. To check the validity of this new inversion algorithm, several numerical tests are conducted. The results show that this new source rupture process inversion algorithm is computa-tionally efficient and numerically stable, and depends less on the initial model compared with the two popular inversion methods, i.e. the linear matrix method and the global stochastic search method. Therefore, this new inversion algorithm is expected to be useful in inverting earthquake rupture processes.
Based on the stochastic AMR model, this paper constructs man-made earthquake catalogues to investigate the property of parameter estimation of the model. Then the stochastic AMR model is applied to the study of several strong earthquakes in China and New Zealand. Akaike′s AIC criterion is used to discriminate whether an accelerating mode of earthquake activity precedes those events or not. Finally, regional accelerating seismic activity and possible prediction approach for future strong earthquakes are discussed.
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 Mw7.6, 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 inver- sion result via comparing with the GPS observations and discussed its scientific signification.
Using multifractal spectrum estimating method based on the wavelet, the multifractal characteristics of GSR of earthquakes in China, Japan and New Zealand regions have been studied. It is shown that the multifractal spectra of GSR are obviously different in inter- and intra- plate regions. Moreover, though Japan and New Zealand are all located at the boundary of plates, West and East China are all characterized of continental tectonic structure, the multifractal spectra of GSR for both the two regions are also different. Further analysis shows that the natures of multifractal spectra of GSR are somehow related to the complexity of tectonics.
