An Ms7.0 earthquake struck Jiuzhaigou county at 9∶19 pm on August 8,2017 in Aba Prefecture of Sichuan Province.The epicenter was located in the intersection area of the Huya fault on the east boundary of the Bayan Har block and the Tazang fault on the east section of the East Kunlun fault,with complicated seismotectonic settings.This earthquake caused damages to houses and roads,and landslides collapsed.According to the data of high-resolution satellite image interpretation,the measurement data of tectonic deformation and dating data,it shows that the east section of the Tazang fault has been dominated by left-lateral strike-slip accompanied with thrust faulting;the horizontal sliding rate is about 2.7 ～ 4.1 mm/yr,and the vertical sliding rate is about 0.56 ～0.6 mm/yr.Combined with the distribution of major earthquake and aftershocks and the results of major earthquake source mechanism solution,a three-dimensional seismic structure model is established.The analysis reveals that this earthquake belongs to strike-slip earthquake with the main rupture angle of 57° ～77°.It was caused by the eastward push of the Qinghai-Tibet Plateau mass,and the seismogenic fault may be a branch of the Tazang fault.According to the study of historical earthquakes,active faults and deformation observation,the Bayan Kala block has significant strong earthquake tectonic background,and it is necessary to continue to pay attention to the seismic activity and deformation of the boundary of the block.%2017年8月8日21时19分,四川阿坝州九寨沟县发生7.0级地震,震中位于巴颜喀拉块体东边界虎牙断裂和东昆仑断裂带东段塔藏断裂交汇区域,地震构造背景较为复杂.地震导致了房屋和道路破坏、滑坡崩塌.根据高分辨率卫星影像解译、阶地坎变形的测量和测年数据得到:塔藏断裂东段晚第四纪以来以左旋走滑为主,兼逆分量,水平滑动速率为2.7 ～4.1 mm/yr,垂直滑动速率为0.56～0.6 mm/yr.结合此次地震的主余震分布、主震震源机制解等综合结果,初步建立了三维发震构造模型,分析认为此次地震属于走滑型地震,主破裂倾角57° ～77°,发震断层可能是塔藏断裂的一条分支,是青藏高原块体向东推挤的一次地震事件.基于历史地震、活动断裂和形变观测方面的研究,巴颜喀拉块体具备显著的强震构造背景,对于该块体边界带周缘的强震活动和变形需要继续关注.
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