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本文利用远震P和SH波反演得到2008年5月12日汶川大地震(MW=7.9)的一系列有限破裂模型。使用一种基于小波变换的模拟退火非线性反演方法,我们将主断层划分成若干个子断层,在反演时同时确定每个子断层上的滑移量、滑动角、上升时间(risetime)以及平均破裂速度。我们首先根据一个假定的破裂模型生成理论地震图,将该理论地震数据作为输入进行反演,对该有限破裂反演方法进行了一系列测试,以验证反演对断层倾角、平均破裂速度、最大破裂深度等参数的敏感性。然后我们采用4个不同倾角的断层面来对汶川地震远震体波记录进行反演。结果表明,若对只在一个断层面上模拟该地震,30°倾角是个较为合适的值。反演的结果还表明,此次地震有两个主要的能量释放区域,并且主断层面存在倾角变化的可能性。在将来的研究中,可以结合GPS,InSAR测地学以及强震等数据,来对强震的破裂过程做更细致的研究。
In this paper, a series of finitely rupture models of Wenchuan Earthquake (MW = 7.9) on May 12, 2008 are obtained by teleseismic P and SH wave inversion. Using a simulated annealing nonlinear inversion method based on wavelet transform, we divide the main fault into several sub-faults, and at the same time, determine the slippage, sliding angle, risetime and average Rupture speed. We first generate a theoretical seismogram based on a hypothetical rupture model, invert the theoretical seismic data as input, and conduct a series of tests on the finite-rupture inversion method to verify that the inversion has the greatest effect on the dip and average rupture velocity of the fault Rupture depth and other parameters of the sensitivity. Then we use four fault planes with different inclinations to invert the teleseismic body wave records of Wenchuan earthquake. The results show that the 30 ° dip is a suitable value if the earthquake is simulated on only one fault plane. The inversion results also show that there are two major energy release areas in this earthquake and the possibility of dip changes in the main fault. In future research, we can combine the data of GPS, InSAR geodesy and strong earthquakes to study the rupture process of strong earthquakes more carefully.