Abstract: The kinematic property of the Wenchan earthquake's surface rupture changes from strike-slip with slightly smaller dip-slip component to the dominant dextral strike-slip at the northeasternmost region between Shikan in Pingwu county and Woqian in Qingchuan county,where,the dip-slip component is reverse between Shikan and Pingxi,normal at Kuangpingzi and its north,with no compressive deformation observed,and it turns to dextral strike-slip near Woqian.The width of the surface deformation zone is less than 10m on this segment.At Dongjia,a village north of Woqian in Qingchuan,the seismic surface rupture zone mainly exhibits as extensional fissures and graben-like negative landform,which are the products of accommodation of the heterogeneous stress and strain at the tip portion of the seismic surface rupture.The width of the surface deformation zone is about 10～12m.No surface rupture evidence was found at Donghekou village in Qingchuan county,so we infer that the surface rupture zone didn't spread through the Qingshui River flowing along the three villages of Donghekou,Guanzhuang and Liangshuijing in Qingchuan county and the structural geomorphology reflects variant vertical motion.Evidence for dextral strike-slip motion was hardly found.The whole length of the rupture zone on the central fault is around 240km.In the course of the Wenchuan earthquake,the tectonic deformation on the surface along the central fault was adjusted within the range of the central fault,and didn't transfer to the external regions.

Key words: Wenchuan M_S 8.0 earthquake, surface rupture, the central fault, rupture(deformation)at tip portion, Qingchuan

摘要： 汶川地震地表破裂在东北端从石坎子乡到窝前的运动性质存着从走滑分量略高于倾滑分量到完全为右旋走滑运动的变化过程,倾滑分量在石坎子—平溪段具有逆断性质,在矿坪子及其以北为正断性质,未见挤压变形,窝前完全为右旋走滑运动,地表变形带宽度集中在10m以内;在董家村,地震地表破裂带主要表现为张性裂缝及地堑式负地形,是地震破裂在尾端应力作用下,应变不均一性调节的产物,地表变形带宽度约10～12m;在东河口以北未见地表破裂的证据,推测汶川地震地表破裂带没有穿过流经青川县东河口、关庄、凉水井一带的清水河,东河口一带的构造地貌现象反映了垂直差异性运动,不存在右旋走滑运动的地质地貌证据。在中央断裂东北端断层一侧隆升和另一侧拉张的典型四象限格局成为汶川地震地表破裂的端部表现特征。中央断裂上的汶川地震地表破裂带总长度为240km左右。在汶川地震过程中,沿着中央断裂在地表产生的构造变形在中央断裂的范围内就已经得到了调整,并没有越过中央断裂的范围而传递到以外的地段。

关键词: 汶川8.0级地震, 地表破裂, 中央断裂, 端部破裂(变形)特征, 青川