汶川M_S 8.0地震平原区地表破裂的初步调查  

PRELIMINARY INVESTIGATIONS ON SURFACE RUPTURE CAUSED BY THE M_s8.0 WENCHUAN EARTHQUAKE IN THE CHENGDU PLAIN AREA

作　　者：李安[1] 杨晓平[1] 陈献程[1] 

机构地区：[1]中国地震局地质研究所国家地震活动断层研究中心,北京100029

出　　处：《第四纪研究》2009年第3期554-564,共11页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:40572126);中国地震局汶川8.0级地震应急科学考察项目资助

摘　　要：2008年5月12日四川省汶川发生M_s8.0级地震,造成龙门山断裂带映秀-北川断裂长达240km和灌县-江油断裂72km的地表破裂。同时在龙门山山前的成都平原内出现了地表弯曲变形、地裂缝、河流跌水以及具有条带状分布的喷砂冒水点和建筑物破坏加剧的现象。为此,对这一地区进行了进一步的调查工作。调查采取以寻访形式为主,结合使用高精度3D扫描仪进行地形测量和探槽开挖。通过调查,发现平原区的隐伏断裂在汶川M_s8.0地震中发生了错动,断层破裂面在地表未见有出露,而是在近地表形成弯曲变形。什邡市师古镇和隐丰镇之间存在两条地震灾害异常带,北北东向灾害异常带长约7km;北北西向灾害异常带长约5km。通过探槽开挖和地形测量得到的汶川M_s8.0级地震在平原区形成的垂直位移为20cm。OR 12th May 2008, the Ms8.0 Wenchuan earthquake occurred in Western Sichuan Province, China. This earthquake generated 240km and 72km-long surface rupture zones along the Beichuan-Yingxiu and the Guanxian - Jiangyou Faults respectively in the Longmenshan Fault zone. The pediment buried fault of the Longmenshan may also have produced rupture near the surface in the Chengdu Plain. Our preliminary field investigations reveal that surface flexural deformation, ground fissures, waterfalls, sand liquefaction points with zonal distribution, and the aggravated building damage and destruction occur between Shigu and Yinfeng towns （31 ° 10′00″ - 31 °06′00″N, 104°02′10″- 104°05′30″E）, Shifang City in the Chengdu Plain. Further investigations, combined with high- precision topographic survey and trench excavation, reveal that dislocation occurred in the the buried fault of the plain area after the earthquake. We totally obtained data of over 22 surface fissures,33 sand liquefaction points,and 12 building damages and deformations. We also excavated two trenches in the north of Linjiayuanzi and Fanjiayuanzi of Shigu Town and measured waterfall scarps and surface flexural deformation in the north of Linjiayuanzi by using 3D laser scanner. Three conclusions are drawn： （1）There are two seismic disastrous zones between Shigu and Yinfeng Towns, Shifang City. One is about 7km-long with the direction of NNE,and the other is about 5km-long with the direction of NNW. Both are related with the pediment buried faults of the Longmenshan. Shallow seismic profile also attested this result. （2）Ruptures were caused in buried fault by the Ms8.0 Wenchuan earthquake,showing not as exposed surface rupture but as flexural deformation near the surface in the Chengdu Plain. （3）The vertical displacement in the plain area reached up to 20cm as revealed by trench excavation and topographic survey.

关 键 词：汶川Ms8.0级地震 地表破裂 褶皱变形 跌水陡坎 成都平原 

分 类 号：P315.2[天文地球—地震学]