东昆仑断裂带东段塔藏断裂几何结构及滑动递减模型讨论

塔藏断裂位于东昆仑断裂带东段,长约170km,与岷山断裂带共同构成巴颜喀拉块体的东北构造边界,中部与岷江断裂、荷叶断裂、虎牙断裂的北延段交会,构成岷山隆起的地貌边界。通过卫星影像解译结合构造地貌调查,确定了断层属于全新世活动断层,并利用断层走向弯曲和活动性、阶区等标志将塔藏断裂分为三段。西段为罗叉段,总体走向NWW,西侧与玛曲断裂形成左行左阶拉分区,东侧在下黄寨村走向顺时针偏转至东北村段。中段为东北村段,总体走向NW,东侧在九寨沟口附近走向逆时针偏转至马家磨段。东段为马家磨段,总体走向NWW,西侧隔荷叶断裂、虎牙断裂的北延段与中段相接。东北村段以岷江断裂斜交点为界可分为南北两个次级段,马家磨段以阶区为界划分为扎如次段、唐寨次段、勿角次段。罗叉段和马家磨段的地震离逝时间较近,东北村段相对较远。断裂带整体呈反"S"形,自西向东滑动速率总体呈减小趋势,大部分水平变形转化为垂向的岷山隆升。结合不同段上的滑动速率,发现东昆仑断裂东段滑动速率呈梯度下降特征与东昆仑断裂带东段断层弯曲的几何特征相对应。

Geometric Structure and Slip Gradient Model of the Tazang Fault in the East Kunlun Fault Zone

The Tazang fault is located in the eastern part of the East Kunlun fault zone with a length of 170 km, which constitutes the northeast border of Bayan Har block with Minshan fault zone. Satellite image and geological survey have revealed evidence for Holocene movement along the fault. The fault can be divided into three sections by the segmental signs of strike-slip fault, such as geometric and tectonic discontinuities in combination of geomorphic features and fault zone materials. The Locha section generally strikes NWW, developed sinistral left-step with Maqu fault in the west, and rotates clockwise on the Xiahuangzhai village in the east. The Dongbei village section generally strikes NW, and rotates anticlockwise on the entrance of Jiuzhaijou in the east. We divided the Dongbei village section into two sub-sections, and the northern and southern sub-sections are separated by the Minjiang fault. The Majiamo section is divided into three sub-sections, namely Zharu, Tangzhai, Wujiao sections. The elapsed time in Loucha and Majiamo sections was relatively short. The linear horizontal slip of the east Kunlun fault zone transforms into the vertical movement of the Minjiang fault zone and Huya fault zone which trends nearly SN~NNE, and the uplift of Minshan. The fault sections splay out from NW to SE that has good correlation with the slip gradients along the east Kunlun fault.