关键词: 地震活动性, 地表构造, 基底断裂, 变形特征, 库车坳陷

Abstract: By analyzing the seismicity in Kuqa depression,north Tarim Basin,some active basement faults are inferred from the distribution of earthquake epicenters in several profiles.The different deformation characteristics between the cover and the basement,as well as their reasons are investigated by comparing the locations of surface structures and basement faults,combined with some other results of deformation and kinematic research in this region.The following conclusions can be drawn from the present study: (1)The distribution of earthquake epicenters indicates that active basement faults exist along the tectonic grain corresponding to that of the surface structures of the Qiulitage-Yaken tectonic belt in Kuqa depression.In the basement beneath the East and West Qiulitage anticlines,there exist the East,North and South Qiulitage deep faults.Moreover,in the basement beneath the Yiqikelike anticline and Yaken anticline there exist the Yiqikelike and Yaken deep faults.These facts may imply that the development of surface structures was controlled by the deep structures. (2)It is revealed that a NE-trending deep strike slip fault is developed along the line from the west end of the Yiqikelike anticline to the Dongqiu No.5 well,and a NW-trending deep fault is developed on the west side of Baicheng.These two active deep faults cut the tectonic grain of the region,and might be responsible for the segmentation of tectonics in Kuqa depression,probably has led to the greater contraction at the middle segment of Kuqa depression(Kuqa-Baicheng)and smaller contraction at east and west segments.(3)The different characteristics of media result in the different deformation between the cover and the basement.The strength of the lithosphere at the basement of Kuqa depression is extremely high,so that deformation of the basement here is dominated by brittle fracturing and the generation of earthquake.The strength of the sedimentary rocks in the cover is much weaker,which may cause the plastic flow of the rocks under the action of long-period intense compression from the orogenic belt.And especially with the existence of coal or salt layers of extremely weak strength in the cover,a large scale aseismic detachment may occur along these weak layers.

Key words: seismicity, surface structure, basement fault, deformation characteristic, Kuqa depression