2000年11月14日东昆仑8.1级地震的构造背景

TECTONIC BACKGROUND OF THE Ms 8.1 EARTHQUAKE ON 14 Nov,2001 AT EAST KUNLUN FAULT

20 0 1年 11月 14日的 8.1级地震发生在东昆仑断裂带西段的一条北西西向走滑断裂上 ,从卫星影像上可以清楚地看到该断裂。断裂沿北西西向的河谷北岸发育 ,是阿尔喀山的南缘断裂 ,断裂构造地貌非常清楚 ,是一条可以发生 8级以上地震的活动断裂。从运动学背景看 ,本次地震的主动盘为断裂的南盘 ,且地震破裂自西向东发展 ,震源深度较浅 ,所以位于断裂北盘和西侧的新疆且末、若羌等距离震中较近的地区 ,地震的震感反映并不明显 ;而震中东侧的格尔木和南侧地区的震感反映较强。从青藏高原活动构造、运动学背景和现有的地震参数分析 ,这次东昆仑 8.1级地震发生在巨大的东昆仑断裂西段 ,由于青藏高原东北部的块体向东逃逸和旋转运动 ,造成断裂左旋扭动的结果。

A massive earthquake happened on 14 Nov at 09∶26∶18 UTC along a NWW slip fault belonging to the western part of East Kunlun Fault (EKF) zone. The fault is clearly visible on satellite images (ETM+ and ASTER). The fault that is along the northern bank of the valley in NWW direction, it is south edge fault of Alk Mountain with typical faulting geomorphology. EKF is indeed an active fault likely to host major earthquake (Ms>8). In the view of the dynamic background, the southern wall of the fault is the active part and the fracturing progressed from west to east and the source of the earthquake is shallow. Therefore the shock was quickly diminished in the north and west direction from the epicenter where Qiemo and Ruoqiang County of Xinjiang not far away from the earthquake experience rather light shock, while the shock in east Geermu of Qinghai Province and south direction was much stronger and extended farther. According to the analysis of the dynamic background of Qinghai-Tibet Plateau active tectonics and the earthquake parameters, this earthquake in the western part of EKF was the result of left lateral rotation caused by the north-east block of Qinghai-Tibet Plateau escaping to the east and related to the clockwise rotation of the block.