SEISMOGENIC STRUCTURE AND RUPTURE MECHANISM OF THE MS 8.0 WENCHUAN EARTHQUAKE

doi:10.3969/j.issn.0253-4967.2012.04.003

Abstract

Abstract:

A composite multiple seismogenic source model is presented to interpret the preparation and generation of the Wenchuan earthquake,based on the results of investigations on the coseismic surface rupture,aftershock distribution and crustal deformation of the Wenchuan earthquake and the studies on the tectonic deformation conducted before the earthquake. It is assumed that the differences in the structure and property of the lithosphere beneath the west Sichuan plateau,Longmen Shan and Sichuan Basin led to the differences in deformation behavior and stress accumulation between them,and their joint actions resulted in the high accumulation and abrupt release of stress in the Longmen Shan Fault zone,witch eventually generated the Wenchuan mega-earthquake. As a high-friction high-angle listric thrust,the Longmen Shan Fault zone is not liable to deformation(but high stress accumulation)to form "slip deficit zones" before earthquake,or to micro-rupturing to form "seismic gaps" before earthquake. When stress accumulated exceeded the strength of the Longmen Shan Fault zone,burst occurred,creating the huge earthquake. Coseismic deformation and energy release were concentrated mainly in the Longmen Shan Fault zone to offset the pre-earthquake "slip deficit" and "seismic gap".The high-angle listric thrust structure of the seismogenic fault of the Wenchuan earthquake played an important role in controlling the preparation and generation of the Wenchuan earthquake. The decrease of normal stress resulting from increased displacement rate on the fault plane was the major contributor to the rupture of the high-angle listric thrust fault.

Key words: Wenchuan earthquake, Seismogenic fault, rupture process

摘要：

通过对汶川地震同震地表破裂、余震分布、地壳形变等的考察以及震前构造变形的研究,提出了汶川地震孕育和发生的多单元组合模型,认为川西高原、龙门山和四川盆地岩石圈结构及性质的差异造成了它们在变形方式和应力积累上的差异,其共同作用导致了龙门山断裂带应力的高度积累和突发释放,形成了汶川特大地震。龙门山断裂带具有高摩擦强度和高角度铲型逆冲结构,使得其不仅不易发生变形(但能积累很高的应力)形成震前的 "滑动亏损带",而且不易发生微破裂形成震前的 "地震空区"。当应力积累超过龙门山断裂带的强度时,就突发破裂形成巨大地震,同震变形和能量释放主要发生在龙门山断裂带,补偿震前的 "滑动亏损"、填满震前的 "地震空区"。汶川地震发震断裂的高角度铲型逆冲结构对于汶川地震的孕育和发生起着重要的控制作用,断裂面上位移加速导致的正应力下降是高角度铲型逆冲断裂发生破裂的重要原因。

关键词: 汶川地震, 发震构造, 破裂机理

CLC Number:

P315.2

ZHANG Pei-zhen, ZHU Shou-biao, ZHANG Zhu-qi, WANG Qing-liang. SEISMOGENIC STRUCTURE AND RUPTURE MECHANISM OF THE M_S 8.0 WENCHUAN EARTHQUAKE[J]. SEISMOLOGY AND GEOLOGY, 2012, (4): 566-575.

张培震, 朱守彪, 张竹琪, 王庆良. 汶川地震的发震构造与破裂机理[J]. 地震地质, 2012, (4): 566-575.

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SEISMOGENIC STRUCTURE AND RUPTURE MECHANISM OF THE M_S 8.0 WENCHUAN EARTHQUAKE

汶川地震的发震构造与破裂机理

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