龙门山彭县-灌县断裂的活动构造与地表破裂  

ACTIVE TECTONICS AND SURFACE RUPTURE OF THE PENGXIAN- GUANXIAN FAULT,LONGMEN MOUNTAIN,SICHUAN,CHINA

作　　者：李勇[1] 黄润秋[2] A.L.Densmore 周荣军[4] 闫亮[1] N.Richardson 董顺利[1] M.A.Ellis 张毅[1] 何玉林[1,4] 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,成都610059 [2]成都理工大学地质灾害防治国家重点实验室,成都610059 [3]Institute of Hazard and Risk Research and Department of Geography,Durham University [4]四川省地震局工程地震研究院,成都610041 [5]Department of Earth Science,Swiss Federal Institute of Technology [6]Center for Earthquake Research and Information,University of Memphis

出　　处：《第四纪研究》2009年第3期403-415,共13页Quaternary Sciences

基　　金：国家自然科学基金应急项目(批准号:40841010);中国地质调查局应急项目

摘　　要：2008年5月12日在龙门山发生了8.0级特大地震,彭县-灌县断裂亦发生了同震地表破裂。在前期对龙门山活动构造研究的基础上,汶川特大地震发生后,在灾区进行了多次的野外调查和国际合作考察,重点对汶川地震的地表破裂和地质灾害开展了详细的详细野外地质填图,利用全站仪和GPS对地表破裂进行了精确的测最,研究了的地表破裂地貌错位、构造组合和运动学,已实地测得地表破裂数据70余组(其中彭县-灌县断裂地表破裂数据20余组)。文章以彭县-灌县断裂地表破裂为切入点,在彭县-灌县断裂的关键部位开展了详细的野外地貌测量,主要测量了彭州磁峰、白鹿、绵竹金花和汉旺等地的地表破裂,标定了彭县-灌县断裂破裂带的垂向断距和水平断距,结果表明该地表破裂南西起于彭州磁峰,向北东延伸经白鹿、绵竹金花至绵竹汉旺,全长约40～50km。地表破裂带沿彭县-灌县断裂带的走向断续分布,单个破裂长度在几米到500余米不等,破裂带切割了多种类型的地貌单元,包括山脉基岩、河流阶地、冲洪积扇、公路、桥梁等,同时也使道路发生拱曲、破坏和桥梁垮塌或移位。其以脆性破裂为特征,以逆冲-右旋走滑为特点,断面倾角较陡,北西盘为上升盘,南东盘为下降盘,垂直位错介于0.39～2.70m之间,水平位错介于0.20～0.70m,平均垂直位错为1.6m,平均水平位错为0.6m;地表最大错动量的地点位于彭州白鹿镇,其中最大垂直断错为2.7±0.2m,最大水平断错为0.7±0.2m。垂直位错与水平位错量之间的比值为2:1,表明该地震地表破裂带不仅存在逆冲运动分量和右旋走滑运动分量,而且逆冲运动分量大于右旋走滑运动分量,显示了彭县-灌县断裂破裂带具有以逆冲和缩短作用为主、右旋走滑作用为辅的破裂性质。其与映秀-北川断裂带的地表破裂相比较,该断裂的地表破裂程度远小于映秀-北川断�The Ms 8.0 Wenchuan Earthquake of May 12th,2008 occurring in Longmen Mountain caused surface rupture in the Pengxian - Guanxian Fault. After the earthquake we carried out several field surveys in Cifeng Town and Bailu Town of Pengzhou City and Jinhua Town and Hanwang Town of Mianzhu County, focusing on detailed geological mapping in typical surface rupture and active fault belts and precise measurements by GPS and EDM. The Pengxian - Guanxian Fault after the Wenchuan Earthquake is characterized by fragility, showing surface rupture cutting a wide range of terrain units. We measured the vertical and horizontal offsets of the Pengxian - Guanxian Fault in some key positions. The surface rupture started from Xiang＇e Town of Dujiangyan City,extended through Cifeng, Bailu, Jinhua, Hanwang, and to Sangzao Town of Anxian County, with a total distance of about 40 - 50km. It is characterized by dextral strike-slips and steep dipping. The upthrown block was in the northwest while the downthrown in the southeast. The largest measured rupture is located in Bailu Town, of 2.7 ± 0.2m vertical offset and 0.7± 0.2m horizontal offset respectively. The vertical offset was 0.39 -2.70m and the horizontal offset was 0.20 -0.70m with the average of 1.6m and 0.6m respectively,indicating the existence of thrust displacement and dextral strike-slip displacement. The ratio of thrusting to strike-slipping is 2 ： 1 in the Pengxian - Guanxian Fault,which indicates that the thrust displacements are twice more than the dextral strike-slip displacements. Compared with the surface rupture of the Yingxiu - Beichuan Fault, the the Pengxian - Guanxian Fault rupture is far less remarkable： it is shorter,with smaller less vertical and the horizontal offsets and mainy of thrust displacement. It suggests that the surface rupture of Wenchuan Earthquake consists of two paralleled thrust faults linked by the Xiaoyudong Fault,while the subsurface rupture consists of two imbricate thrust faults.

关 键 词：汶川地震 地表破裂 彭县-灌县断裂 逆冲-走滑作用 龙门山 

分 类 号：P315.2[天文地球—地震学]