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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。
On May 12, 2008, an M_s8.0 earthquake occurred in Wenchuan, Sichuan Province, causing surface ruptures in the Longmenshan fault zone of Yingxiu-Beichuan fault up to 240km and in Guanxian-Jiangyou fault of 72km. In the meantime, surface bending deformation, ground fissures, river water fall, sandblasting and water-taking with banded distribution and aggravation of buildings have occurred in the Chengdu Plain in front of Longmen Mountain. To this end, further investigation was carried out in this area. The survey was conducted mainly on the basis of the search form, combined with the use of high-precision 3D scanners for topographic surveying and trench excavation. Through the investigation, it is found that the hidden faults in the plain area have been dislocated in the M_s8.0 Wenchuan earthquake. There is no surface rupture on the fault rupture surface, but bending deformation occurs near the surface. There are two seismic disaster anomalous zones between Shifugu town of Shifang City and Yinfeng Town. The anomalous zone of north-north eastward disasters is about 7km long and the anomaly zone of north-northwestward disasters is about 5km long. The Wenchuan M_s8.0 earthquake, which was obtained through trench excavation and topographic survey, formed a vertical displacement of 20 cm in the plain area.