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本文利用全球地震台网(GSN)的宽频带与长周期地震波形资料,采用矩张量反演的新方法,反演得到了2008年5月12日四川省汶川县MS8.0地震及其7个较大余震(MS5.0—6.0)的矩张量解与震源时间函数等震源参数.文章首先简要叙述矩张量反演新方法的理论背景和技术途径,并以汶川大地震的一个余震为例阐述了具体的实现过程;然后给出包括主震在内的8次地震的矩张量解和震源时间函数;最后分析探讨这些结果的构造意义.本文提出的矩张量反演新方法,不但与全球矩心矩张量(GCMT)一样,可以给出点源矩张量解,而且还可以给出点源的震源时间函数.反演得到的汶川大地震的7个较大余震的震源时间函数表明,即使是中等强度的地震也可能有复杂的震源过程;汶川大地震的多数余震发生在以逆冲为主、兼具小量走滑分量的龙门山断裂带的主断裂上,但很可能有些余震则发生在主断裂附近的次级走滑断裂上.
In this paper, a new method of moment tensor inversion is applied to the broadband and long-period seismic waveform data of the Global Seismograph Network (GSN). The MS8.0 earthquake in Wenchuan County, Sichuan Province on May 12, 2008 and its 7 (MS5.0-6.0) moment source tensor solution and source time function, etc.The article first briefly describes the theoretical background and technical approaches of a new method of moment tensor inversion, and takes an aftershock of Wenchuan Earthquake As an example to illustrate the concrete realization process. Then, the moment tensor solution and the source time function of eight earthquakes including the main shock are given. Finally, the constructive significance of these results is analyzed. A new method of moment tensor inversion , Not only the global moment of mind tensor (GCMT), can give the point source moment tensor solution, but also can give the source time function of the point source.The retrieved large aftershocks of Wenchuan earthquake The source time function shows that even the moderate-intensity earthquakes may have complex source processes. Most aftershocks of the Wenchuan earthquake occurred on the main fault of the Longmenshan fault zone, which was dominated by thrusting and had a small amount of strike-slip component. But it is quite possible that some aftershocks will happen to the Lord Secondary slip near the crack fracture.