【摘要】 2008年5月12日发生的里氏8.0级汶川地震处于龙门山造山带与四川盆地的构造边界上。350km长的地表破裂带呈右行左阶雁行排列在具有逆冲和右行走滑性质的汶川—茂县—青川、映秀—北川和江油—都江堰3条断层带上。下地壳的韧性流动伴随中地壳韧-脆性剪切带应力和应变的积累,产生上地壳脆性发震断层,并控制地表破裂带和滑坡的分布。震源出现在上地壳脆性断层与中地壳脆-韧性剪切带的交汇部位。以汶川地震为例,结合板内地震基本特征,提出引入大陆动力学理论完善工程区域稳定性理论基础,构建基于板块学说、地质力学和大陆动力学理论的相互补充的工程区域稳定性评价体系;对活断层与地震活动性预测提出见解,强调仅仅从活断层的存在及其活动强度来预测地震活动性与强度是远远不够甚至是错误的,必须将下地壳、中地壳和上地壳结构作为一个整体加以研究和判别;提出工程区域地壳稳定性评价指标体系,指出了大陆内部"安全岛"划分应采用的核心指标。更多还原

【Abstract】 The Wenchuan earthquake of May 12th,2008 on the tectonic margin between the Longmenshan orogenic belt and Sichuan basin had a magnitude of 8.0 Ms,on the Yingxiu-Beichuan fault.A 350-km-long surface rupture zone exhibits right-lateral and left-step features.It is related to the west-dip Wenchuan-Maowen-Qingchuan fault,Yingxiu-Beichuan fault and the Jiangyou-Dujiangyan fault which show dextral strike-slip and thrust.The brittle seismogenic faults in the upper crust,which controlled surface rupture zones and landslides,were produced by slowly ductile flow of lower crust with the stress and strain accumulation at the ductile-brittle shear zone of the middle crust.Seismic source locates at the connection spot between the ductile-brittle shear zone in middle crust and brittle active faults in upper crust.This paper examines the Wenchuan Earthquake in association with the basic characters of intra-plate earthquake.It is believed that it is necessary to develop the theory of regional stability for engineering by continental dynamic theory.The evaluating system must be established together by plate theory,geological mechanics and continental dynamic theory.Some opinions about active faults and earthquake prediction are discussed.It is stressed that earthquake prediction only by active fault is insufficient or improper.The causative structure in lower crust,ductile-brittle transition zone in middle crust and brittle seismogenic faults in upper crust must be considered as a whole in the study.At last,an evaluation index system of regional crustal stability for engineering projects is put forward and the key index for "safety island" is pointed out.更多还原