关于汶川地震发震机制  

On the Triggering Mechanics of Wenchuan Earthquake

作　　者：卢华复[1] 贾东[1] 王良书[1] 王胜利[1] 

机构地区：[1]南京大学地球科学与工程学院,江苏南京210093

出　　处：《高校地质学报》2008年第2期133-138,共6页Geological Journal of China Universities

摘　　要：2008年5月12日汶川8级地震的发震断层是四川龙门山逆冲带的前锋灌县—安县断层,或此断层附近新产生相同产状的断层。发震断层走向NE倾向NW,逆冲兼右行平移。汶川地震的发震机制是印藏陆-陆碰撞后,印度次大陆活塞状嵌入欧亚板块造成青藏高原东部向SEE方向近水平挤压,在龙门山冲断带前锋向东南逆冲到四川盆地,构造应力积累和释放的结果。汶川地震演示了一个青藏高原东缘龙门山隆起的构造模型,即其经由龙门山冲断带的地壳冲断作用和缩短作用而隆升。这与Burchfiel的模型不同,该模型认为龙门山上升是由于韧性下地壳流受到四川盆地高强度地壳阻挡而上涌所致。这两种模型可能各有其适用时间阶段,然而本文的模型是不可或缺的,因汶川地震已显示了它的真实性。The triggering fault of Ms 8.0 Wenchuan earthquake on May 12th, 2008 is the Guanxian-Anxian fault, the frontal thrust of the Longmenshan thrust belt, or a newly created fault near the Guanxian-Anxian fault with the similar attitude. The triggering fault is a NE trending, NW dipping and mainly of thrusting with dextral strike slip fault. The Wenchuan earthquake is resulted form the tectonic stress accumulation and release in the frontal fault of Longmenshan thrust belt caused by the SEE ward horizontal compression from the eastern Tibet plateau including the Longmenshan toward the northwest margin of Sichuan basin, and the SEE ward horizontal compression is led by the indentation collision and subducton of India continent against the Tibet plateau after the continent-continent collision 50 Ma B.P., which resulted to the crust movement from NNE to NE to NEE to SEE gradually from middle Tibet to eastern Tibet. The Wenchuan earthquake leds to a tectonic model of uplifting of the eastern margin of Tibet plateau, the Longmenshan Mountians, through the upper crust thrusting and shortening in the Longmenshan thrust belt. That is basically different from Burchfiel＇s model about the Longmenshan uplifting resulted from the ductile lower crust flow eastwart barred by strong Sichuan basin crust and become upwelling. Probably both models worked in the different stages of the Longmenshan uplifting respetively, but our model is essential because We have seen it worked in the Wenchuan earthquake.

关 键 词：汶川地震 发震断层 龙门山前锋断层 逆冲兼右行走滑断层作用 

分 类 号：P546[天文地球—构造地质学]