四川汶川Ms 8.0级地震同震变形特征和分段性

汶川地震发育2条地表破裂带，一条沿中龙门山活动断裂带分布，另一条沿前龙门山活动断裂带分布，前者长超过200km，后者长约80km。同震变形在地表表现为逆冲膝折带，走向N45～60°E，形成公路路面隆起和农田陡坎。逆冲膝折带西北侧抬高，东南侧下降。在剖面上冲断带倾向北西，倾角50～60°。膝折带两侧相对高差沿映秀－北川断裂一般为2.5～3.0m，沿都江堰－汉旺断裂为1.5～1.1m。沿中龙门山活动断裂带，同震变形运动方式具有明显的分段性，映秀－擂鼓镇段，表现为逆冲，走滑现象不明显；北川－青川段既有逆冲又有右旋走滑分量。沿前龙门山活动断裂带，同震变形运动方式主要表现为逆冲，走滑位移和分段性不明显。

Co-seismic Deformation Features and Segmentation of the Ms 8.0 Wenchuan Earthquake in Sichuan

There are two seismic fractured zones developed when the Wenchuan earthquake happened. One occurred along the active fault-zone in the central Longmen Mts. and the other in the front of Longmen Mts.. The length of which is more than 200km and about 80km respectively. The co-seismic deformation shows thrust flexural belt with strike of N45°~60°E in the ground, which caused uplift at its northwest side and subsidence. The fault face dips to northwest with dip angle ranged from 50° to 60°. The vertical offset of the flexural belt ranges 2.5-3.0m along Yingxiu-Beichuan seismic fault, and 1.5-1.1m along Doujiangyan-Hanwang fault. Movement of co-seismic deformation presents obvious segmented features along the active fault-zone in the central Longmen Mts., for instance, in the section from Yingxiu to Leigu town, thrust without evident slip occurred; while from Beichuan to Qingchuan, thrust and dextral strike-slip both happened. But main movement along the front Longmen Mts shows thrust without slip and segmented features.