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| Spatio-temporal variation and focal mechanism of the Wenchuan MS8.0 earthquake sequence |
| Wanzheng Cheng, Zhiwei Zhang, Xiang Ruan |
| Earthquake Prediction Institute, Earthquake Administration of Sichuan Province, Chengdu 610041, China |
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Abstract Based on abundant aftershock sequence data of the Wenchuan MS8.0 earthquake on May 12, 2008, we studied the spatio-temporal variation process and segmentation rupture characteristic. Dense aftershocks distribute along Longmenshan central fault zone of NE direction and form a narrow strip with the length of 325 km and the depth between several and 40 km. The depth profile (section of NW direction) vertical to the strike of aftershock zone (NE direction) shows anisomerous wedgy distribution characteristic of aftershock concentrated regions; it is related to the force form of the Longmenshan nappe tectonic belt. The stronger aftershocks could be divided into northern segment and southern segment apparently and the focal depths of strong aftershocks in the 50 km area between northern segment and southern segment are shallower. It seems like ‘to be going to rupture’ segment. We also study focal mechanisms and segmentation of strong aftershocks. The principal compressive stress azimuth of aftershock area is WNW direction and the faulting types of aftershocks at southern and northern segment have the same proportion. Because aftershocks distribute on different secondary faults, their focal mechanisms present complex local tectonic stress field. The faulting of seven strong earthquakes on the Longmenshan central fault is mainly characterized by thrust with the component of right-lateral strike-slip. Meantime six strong aftershocks on the Longmenshan back-range fault and Qingchuan fault present strike-slip faulting. At last we discuss the complex segmentation rupture mechanism of the Wenchuan earthquake.
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Received: 28 August 2008
Published: 10 April 2009
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| Fund:National Key Basic Research 973b and National Scientific Technology Support Plan (2006BAC01B02-01 -01) |
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Corresponding Authors:
Wanzheng Cheng
E-mail: chengwz@eqsc.gov.cn
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| [1] |
Yu Wang, Shengli Ma, Toshihiko Shimamoto, Lu Yao, Jianye Chen, Xiaosong Yang, Honglin He, Jiaxiang Dang, Linfeng Hou, Tetsuhiro Togo. Internal structures and high-velocity frictional properties of Longmenshan fault zone at Shenxigou activated during the 2008 Wenchuan earthquake[J]. Earthquake Science, 2014, 27(5): 499-528. |
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