Upper crustal velocity and seismogenic environment of the M7.0 Jiuzhaigou earthquake region in Sichuan, China

查看全文 作　　者：DaHu [1]Li;ZhiFeng [2]Ding;Yan [3]Zhan;PingPing [3]Wu;LiJun [2]Chang;XiangYu [3]Sun

机构地区：[1]Chengdu Institute of the Tibetan Plateau Earthquake Research,China Earthquake Administration,Chengdu 610041,China;[2]Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;[3]Institute of Geology,China Earthquake Administration,Beijing 100029,China

出　　处：《Earth and Planetary Physics》索引2021年第5卷第4期,共14页

基　　金：This research was supported by the National Natural Science Foundation of China(No.41974066,No.41474057);ChinArray Project-Northern Section of South-North Seismic Belt(201308011);Project of Science for Earthquake Resilience(XH20051);the Science and Technology Innovation Fund of Sichuan Earthquake Administration(201804). 摘　　要：On August 8,2017,a magnitude 7.0 earthquake occurred in Jiuzhaigou County,Sichuan Province,China.The deep seismogenic environment and potential seismic risk in the eastern margin of Tibetan Plateau have once again attracted the close attention of seismologists and scholars at home and abroad.The post-earthquake scientific investigation could not identify noticeable surface rupture zones in the affected area;the complex tectonic background and the reason(s)for the frequent seismicity in the Jiuzhaigou earthquake region are unclear.In order to reveal the characteristics of the deep medium and the seismogenic environment of the M7.0 Jiuzhaigou earthquake region,and to interpret the tectonic background and genesis of the seismicity comprehensively,in this paper,we have reviewed all available observation data recorded by the regional digital seismic networks and large-scale,dense mobile seismic array(China Array)for the northern section of the North-South Seismic Belt around Jiuzhaigou earthquake region.Using double-difference seismic tomography method to invert the three-dimensional P-wave velocity structure characteristics of the upper crust around the Jiuzhaigou earthquake region,we have analyzed and discussed such scientific questions as the relationship between the velocity structure characteristics and seismicity in the Jiuzhaigou earthquake region,its deep tectonic environment,and the ongoing seismic risk in this region.We report that:the P-wave velocity structure of the upper crust around the Jiuzhaigoug earthquake region exhibits obvious lateral inhomogeneity;the distribution characteristics of the shallow P-wave velocity structure are closely related to surface geological structure and formation lithology;the M7.0 Jiuzhaigou earthquake sequence is closely related to the velocity structure of the upper crust;the mainshock of the M7.0 earthquake occurred in the upper crust;the inhomogeneous variation of the velocity structure of the Jiuzhaigou earthquake area and its surrounding medium appears to be the deep structural factor controlling the spatial distribution of the mainshock and its sequence.The 3D P-wave velocity structure also suggests that the crustal low-velocity layer of northeastern SGB(Songpan-GarzêBlock)stretches into MSM(Minshan Mountain),and migrates to the northeast,but the tendency to emerge as a shallow layer is impeded by the high-velocity zone of Nanping Nappe tectonics and the Bikou Block.Our results reveal an uneven distribution of high-and low-velocity structures around the Tazang segment of the East Kunlun fault zone.Given that the rupture caused by the Jiuzhaigou earthquake has enhanced the stress fields at both ends of the seismogenic fault,it is very important to stay vigilant to possible seismic hazards in the large seismic gap at the Maqu-Maqên segment of the East Kunlun fault zone. 关键词：the M7.0 Jiuzhaigou earthquake 3D P-wave velocity structure deep tectonic seismogenic environment

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Upper crustal velocity and seismogenic environment of the M7.0 Jiuzhaigou earthquake region in Sichuan, China

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