昆仑山地震地表破裂带东段几何学与运动学

Geometry and kinematics in the east segment of the surface rupture zone occurring during the Kunlun earthquake

2001年11月14日,昆仑山脉的西部发生Ms8.1级地震,地表形成的地震破裂带沿袭先存东昆仑断层从西向东延伸350km左右,直至昆仑山口以东逐渐消失。地震破裂带东段(即昆仑山口段)长约90km左右,破裂带宽度10～30m。根据不同地段地表破裂带几何轨迹结构、位移和变形差异,昆仑山口段地震破裂带可划分为4个次级段。其几何轨迹结构样式可分为3类:①双重主破裂连接结构;②单主破裂弧形扩展连接结构;③无破裂连接结构。根据主断面擦痕、破裂带两侧横向冲沟位移标志和分支破裂变形组合关系判断,主破裂表现为左旋走滑运动,而大多数分支破裂(R断层)则表现为左旋走滑兼张性;破裂带最大左旋位移4m左右,破裂带表现为脆性变形,以破裂扩展、块体位移为主,从西向东变形逐渐减弱,直至消失,表现为地震破裂东延扩展前锋特征。

The western Kunlun Mountains was hit by an earthquake of Ms=8.1on November14,2001.A rupture zone occurring on the surface extended for～350km along the pre-existing East Kunlun fault eastward to the east of the Kunlun Pass and then disappeared gradually.The eastern segment (i.e.the Kunlun Pass segment )of the rupture zone is～90km long and10.30m wide.According to the geometri-cal trace patterns ,displacements and differences in deformation in different parts of the surface rupture zone,the Kunlun Pass segment may be divided into four parts and three geometric trace patterns may be distinguished:①the duplex connecting structure of main ruptures;②the connecting structure of arcuate propagation of single main ruptures:③the connecting structure without ruptures.According to the stria-tions on the main rupture planes,offsets of gullies on two sides of the rupture zone and deformation as-sociation of branching ruptures,it may be judged that the movement of the surface ruptures zone is left-lateral strike-slip movement ,while most branching ruptures(R faults)show left-lateral strike-slip and ten-sile features.The maximum left-lateral strike-slip displacement is～4m.The surface ruptures zone is char-acterized by brittle deformation,mainly in forms of rupture propagation and block movement and locally folding and thrusting.The deformation attenuates eastward until its disappearance,exhibiting the character-istics of eastward propagation of the front of ruptures.