An earthquake with Ms7.0 occurred in Jiuzhaigou County,Sichuan Province on 8 August 2017.This work derives the coseismic deformation field based on Sentinel-1 SAR images by using the InSAR technique.Then,the coseismic slip distribution is inverted and the static Coulomb stress changes in the aftershock distribution area and surrounding faults are calculated.Finally,we discuss the seismogenic fault of this event.The results show that from the InSAR deformation fields,the Jiuzhaigou earthquake caused crustal deformation with a magnitude of 20 cm in the line of sight direction.The coseismic deformation fields exhibit an asymmetric characteristic.The coseismic slip was dominated by left-lateral strike motion and mainly distributed at depths 4～16 km,with the maximum slip of approximately 77 cm at a depth 9 km.The inverted magnitude is approximately Mw6.46.The causative fault did not rupture the surface.Most of the aftershocks occurred in the regions with increases of Coulomb stress change.This earthquake increased the Coulomb stress change on some surrounding faults,such as eastern segment of the Dongkunlun fault,Longriba fault,and Huya fault.The seismic risk of the eastern segment of the Dongkunlun fault should be considered in the future.Our work suggests that the causative fault of the Jiuzhaigou earthquake is the Shuzheng fault,which is presumably the hidden part of the northwestward extension of the Huya fault.And this event was resulted from southeastward motion of the Bayan Har block when blocked by the South China block.%2017年8月8日四川省九寨沟县发生Ms7.0地震.本文基于Sentinel-1 SAR影像,利用InSAR技术获取了此次地震的同震形变场,反演获得同震滑动分布,计算了同震位错对余震分布和周边断层的静态库仑应力变化,并对发震构造进行了分析讨论.结果表明:①InSAR同震形变场显示,九寨沟地震造成地表形变最大量级约为20 cm(雷达视线方向),同震形变存在非对称性分布特征.②同震位错以左旋走滑为主,主要发生在4～16 km深度,最大滑动量约为77 cm,位于9 km深处.反演得到的矩震级为Mw6.46.同震错动未破裂到地表.③大部分余震发生在库仑应力增加区.此次地震增加了震中周边地区—些断裂的库仑应力,如东昆仑断裂带东段、龙日坝断裂、虎牙断裂等.④东昆仑断裂东段的未来地震危险性值得关注.⑤九寨沟地震的发震断层为树正断裂,可能是虎牙断裂的北西延伸隐伏部分,此次地震是巴颜喀拉块体南东向运动受到华南块体的强烈阻挡过程中发生的一次典型构造事件.
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