西藏中部格仁错断裂带错嘎错-那拉错段细结构及活动性

STRUCTURE AND ACTIVITY BETWEEN CUOGA CO AND NALA CO OF THE GYARING CO FAULT BELT IN CENTERAL TIBET PLATEAU

通过对格仁错断裂带的错嘎错-那拉错段进行野外调查,先根据该区的地貌及地形变化分析认为河/湖谷北侧断裂带由分布于山坡及坡/冲积物中的一系列正走滑断裂组成。并对错嘎错和那拉错北侧两个综合地质地貌剖面的详细考察结果,重点对断裂活动在地表沉积物中形成的不同方向的派生构造进行了剖析,分析其形成机制与主断裂带几何学和运动学之间的关系,进而判定主断裂的活动性质,根据断裂错动晚更新世以来的坡/冲积物的年龄和冲沟位错,并对断裂活动速率进行了半定量约束,所得断裂在该段活动速率<4mm/a,远远小于前人的估算,并具有相当的正断分量,认为该段这种活动特性是受南北向的申扎-定结地堑系伸展作用的影响结果。

Through our field observation,it was found that the Cuoga Co-Nala Co segment of the Gyaring Co fault belt was a series of normal-dextral strike-slip faults. Two hillside sections north of the two lake of Cuoga Co and Nala Co were in detail studied. The focus was placed on analysis of subtle structures of differently directional sub-faults produced by the main fault. These subtle structures occurred in surface sediments around the main fault and its sub-faults, so they can be observed in deluvium and alluvium as well as in topography. It was found from this analysis that there was considerable normal faulting component in the Gyaring Co fault, which was manly though to be a strike slip fault. And the dating of related deluvium and alluvium and the measuring of their offsets show that the semiquantitative offset rate of the fault since Late Pleistocene would be less than 4mm/a,far lower than the rates given by previous researchers. Characteristics of the Cuoga Co-Nala Co segment suggest that its activity could be affected by extending of the north-south striking Shenzha-Dingjie graben system.