映秀-北川断裂的地表破裂与变形特征  

Surface Rupture and Deformation of the Yingxiu-Beichuan Fault by the Wenchuan Earthquake

作　　者：李勇[1] 周荣军[2] Alexander L.DENSMORE 闫亮[1] Nicholas RICHARDSON 董顺利[1] Michael A.ELLIS 张毅[1] 何玉林[1,2] 陈浩[1] 乔宝成[1] 马博琳[1] 

机构地区：[1]成都理工大学油气藏地质及开发工程国家重点实验室,610059 [2]四川省地震局工程地震研究院,成都610041 [3]Institute of Hazard and Risk Research and Department of Geography,Durham University,Durham,UK [4]Department of Earth Science,Swiss Federal Institute of Technology,Zurich,Switzerland [5]Center for Earthquake Research and Information,University of Memphis,Memphis,Tennessee,USA

出　　处：《地质学报》2008年第12期1688-1706,共19页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号49803013,40372084,40841010);中国地质调查局应急项目;中石化前瞻性项目资助的成果

摘　　要：2008年5月12日在龙门山映秀-北川断裂带发生的8.0级特大地震,属于逆冲—走滑型地震。本文以地表破裂为切入点,在映秀-北川断裂的关键部位开展了详细的野外地貌测量,标定了映秀-北川断裂带的垂向断距和水平断距,结果表明映秀-北川断裂的地表破裂带从映秀向北东延伸达180～190km,走向介于NE30°～50°之间,倾向北西,地表平均垂向断距为2.9m,平均水平断距为3.1m;地表最大错动量的地点位于北川县擂鼓镇,垂直断错为6.2±0.1m,水平断错为6.8±0.2m,逆冲分量与右行走滑分量的比值为3∶1～1∶1,表明该断裂以逆冲—右行走滑为特点,逆冲运动分量略大于或等于右行走滑运动分量。根据近南北向的分段断裂可将映秀-北川断层的地表破裂带划分为两个高值区和两个低值区,其中两个高值区分别位于南段的映秀—虹口一带和中北段的擂鼓—北川县城—邓家坝一带。基于保存于破裂面上的擦痕,我们将该地震破裂过程划分为两个阶段,早期为逆冲作用,晚期为斜向走滑作用。The Ms 8. 0 great earthquake of 12 May 2008 which occurred in the Yingxiu-Beichuan fault of Longmen Mountain belongs to strike-slip-type thrust. With an emphasis on the geomorphic features of the surface ruptures of the great earthquake in Longmen Mountain, the eastern margin of Tibetan Plateau, this paper defines the vertical and horizontal offsets of the Yingxiu-Beichuan fault by detail field geomorphic surveys. The results show that the surface rupture of the Yingxiu-Beichuan fault stretches to NEE direction （NE30°-50°） for 180 - 190 km from Yingxiu to the surface rupture of Beichuan. The average vertical and horizontal offsets are 2.9 m and 3. 1 m, respectively, with the largest vertical and horizontal offsets of 6. 2±0. 1 m and 6. 8 ± 0. 2 m in Leigu town. The ratio of thrusting and dextral slipping in the Yingxiu-Beichuan is 3 ： 1-1：1, indicating that the surface ruptures are characterized with thrusting displacement slightly more than or equal to dextral strike-slip one. Based on the nearly NStrending fault, the surface rupture of the Yingxiu-Beichuan fault can be divided into two segments of large rupture and two segments of small rupture, with the former located at the southern section （Hongkou） and middle section （Leigu） of Yingxiu, Chuanbei county, and Dengjiaba area. We divide the process of seismic rupture into two stages based on the scratch preserved on the fracture planes, early thrusting and later oblique slip motion.

关 键 词：汶川地震 地表破裂 映秀-北川断裂 走滑-逆冲作用 龙门山 

分 类 号：P315.2[天文地球—地震学] P542.3[天文地球—固体地球物理学]