Evidence of sudden rupture of a large asperity during the 2008 Mw7.9 Wenchuan earthquake based on strong motion analysis
Evidence of sudden rupture of a large asperity during the 2008 Mw7.9 Wenchuan earthquake based on strong motion analysis
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DOI：
10.1029/2012gl052516
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发表时间：
2012-09
影响因子：
5.2
通讯作者：
Guohong Zhang;M. Vallée;X. Shan;B. Delouis
中科院分区：
文献类型：
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作者：
Guohong Zhang;M. Vallée;X. Shan;B. Delouis
利用2008年5月12日汶川大地震的26个强震台站的记录，研究了2008年5月12日汶川大地震的破裂过程。进行这一分析所需的波速模型已在余震中得到验证，对于余震，点源假设是一个很好的近似。主震破裂过程的反演证实了以前确定的滑动分布和平均破裂速度（1.3km/s）。然而，本研究中使用的大量数据集清楚地解决了一个非常特殊的行为：位于震中东北20-50公里处的汶川地震的主要滑动区域几乎同时破裂，即地震开始后25秒。这意味着，在这一部分的断层的滑动不能理解的简单的应力释放在破裂前。一个更可能的解释是存在一个强烈的粗糙体，只有当它被应力增加完全包围时才能破裂，导致延迟但残酷的破裂。
We investigate the rupture process of the 12 May 2008 Wenchuan earthquake using the records of 26 strong‐motion stations, located 20–120 km from the seismic fault and with a good azimuthal coverage. The wave velocity model required to conduct this analysis has been validated against aftershocks, for which the point source hypothesis is a very good approximation. The inversion of the main shock rupture process confirms the slip distribution and the average rupture velocity (∼3 km/s) previously determined. However, a very peculiar behavior is clearly resolved by the extensive data set used in this study: the major slip area of the Wenchuan earthquake, located at 20–50 km North‐East of the epicenter, is shown to break almost simultaneously, 25 s after earthquake initiation. This implies that slip in this part of the fault cannot be understood by simple stress release at the rupture front. A more likely interpretation is the presence of a strong asperity, which could break only when it was completely surrounded by stress increase, resulting in a delayed but brutal rupture.