四川汶川Ms 8.0级地震的地表变形与同震位移

Seismic deformation and co-seismic displacement of the Ms 8.0 Wenchuan Earthquake in Sichuan, China

四川汶川Ms 8.0级强烈地震与青藏高原东部松潘-甘孜地块东向挤出导致的龙门山活动断裂右旋斜冲运动存在动力学成因联系。沿龙门山中央北川-映秀断裂发育长度超过250km的地震变形带,由地震陡坎、地震鼓包、地震破裂、地震断层组成,形成了较大的同震位移。在震中区映秀地区观测到的最大同震位移为7.6m,由右旋走滑位移6.1m和垂直位移4.6m2个分量组成;虹口地区的右旋走滑位移为2.7m,垂直位移为4.6m,右旋斜冲总位移为5.3m;北川地区的右旋走滑位移为5.7m,垂直位移为3.4m,右旋斜冲总位移为6.6m;平通地区的右旋走滑位移为3.2m,垂直位移为3.0m,右旋斜冲总位移为4.4m。龙门山前缘的汉旺-漩口断裂及龙门山后缘的茂县-汶川断裂、青川断裂也发生了显著的同震断裂活动,但同震位移小于等于1.0m。根据同震位移实测数据和构造会聚速率的GPS观测资料,估算龙门山地区8.0级地震的复发周期为1150～2950年。

Dextral-slip thrusting of major active faults in Longmenshan Mts. related to eastward extrusion of Songpan-Ganzi terrain in eastern Tibetan Plateau caused the Ms 8.0 Wenchuan Earthquake. Seismic scarps, pressure ridges, seismic fractures and seismic faults formed along Beichuan-Yingxiu fault in central Longmenshan Mrs., and extension of seismic zone along Beichuan-Yingxiu fault exceeds 250kin. Maximum co-scismic displacements with 6.1m dextral slip, 4.6m vertical displacement and 7.6m total displacement occurred in Yingxiu near the seismic epicenter. Co-seismic dextral slip, vertical displacement and total displacement along Yingxiu-Be- ichuan fault are respectively 2.7m, 4.6m and 5.3m in Hongkou, 5.7m, 3.4m and 6.6m in Beichuan, and 3.2m, 3.0m and 4.4m in Pingtong. Minor co-seismic displacement （less than 1.0m） formed along Hanwang-Xuankou fault in east Longmenshan Mts. and Maoxian-Wenchuan fault and Qingchuan fault in west Longmen Mts. though evident seismic faulting occurred along these active faults. Recurrence interval of Ms 8.0 earthquake in Longmen Mts. is estimated to be 1150-2950 years according to maximum coseismic displacement and structural convergent rate determined by GPS.