摘要
2017年8月8日的九寨沟MS7.0地震发生在岷江断裂、塔藏断裂及虎牙断裂交汇地区,地处青藏高原东北部的川甘交界地区,位于巴颜喀拉地块的东缘,地质构造复杂,对于九寨沟地震震中位置和发震断层的确定,存在不同意见.本文利用GNSS及升降轨InSAR观测,在获取九寨沟地震同震形变场的基础上,基于均匀弹性半无限位错模型,联合反演了发震断层的滑动分布模型,并计算了同震库仑应力变化.InSAR同震形变场显示,视线向最大沉降量和抬升量分别为0.21 m和0.16 m,形变场长轴为NW向,形变主要集中在断层西侧.距震中40km和65km的九寨和松潘两县,水平向的GNSS同震位移分别达14.31mm和8.22mm.联合GNSS和InSAR同震形变场反演得到的滑动分布主要集中在沿走向5~33km,倾向2~20km的范围内,平均滑动量为0.18m,最大滑动量为0.91m.发震断层长40km,宽30km,走向155°,倾角81°,滑动角-9.56°.同震位移场及滑移分布模型表明此次地震为一次左旋走滑为主的地震事件,地震破裂并未完全到达地表,与虎牙断裂北段的几何产状和运动学性质更为接近,结合精定位余震的分布,我们确定虎牙断裂北段为此次地震的发震断层,震中位于北纬33.25°,东经103.82°,震源深度10.86km,矩震量为7.754×1018 Nm,相应的矩震级为MW6.5,与美国地调局和哈佛大学给出的震源机制解基本一致.同震库仑应力导致了虎牙断裂北段延长线的东北和西南两端应力增强,其中塔藏断裂的罗叉段和马磨段未来强震的危险性值得关注.
The Jiuzhaigou MS7.0 earthquake of August 8,2017 occurred at the conjunction of theMinjiang,Tazang and Huya faults,the border area between Sichuan and Gansu provinces as well as the northeastern part of the Tibetan Plateau where the tectonics is very complex.There exists a certain controversy about the accurate location of the epicenter and the seismogenic fault for this earthquake.Based on the coseismic deformation field obtained from GNSS and InSAR observations,we inverted for the characteristics of coseismic slip model,spatial distribution and the coseismic Coulomb stress changes using a homogeneous elastic half-space model.The features of coseismic deformation derived from InSAR and GNSS show that this event is dominated by left-lateral strike-slip.The maximum and minimum displacements are about 0.16 mand-0.21 m,respectively,along LOS with the whole deformation field is in the NW direction which is concentrated on the west of the fault.The GNSS horizontal deformation at Jiuzhaigou county and Songpan county,which are of40 km and 65 km away from the epicenter,are 14.31 mm and 8.22 mm,respectively.Slips are mainly distributed in 5~33 km along strike and 2~20 km along down-dip direction.The maximum and average displacements are 0.91 mand 0.18 m,respectively.The seismic rupture did not fully reach the ground surface.The fault plane is 40 km long and 30 km wide with strike angle 155°,dip angle 81°and rake angle-9.56°.These features are consistent with the kinematics and geometry of the northern section of the Huya fault,so we concluded that the northern section of the Huya fault is the seismogenic fault of the Jiuzhaigou earthquake.Results derived from geodetic measurements indicate the epicenter of this event is located at E103.82°,N33.25°with focal depth of 10.86 km and the moment released about 7.754×1018 Nm,corresponding to a magnitude of M_W6.5 which is consistent with that from USGS and GCMT.The coseismic Coulomb stress changes have enhanced the stress on the northeast and southwest of northward extensi
作者
陈威
乔学军
刘刚
熊维
贾治革
李瑜
王阅兵
游新兆
龙锋
CHEN Wei1 , QIAO XueJun1, LIU Gang1 , XIONG Wei1 , JIA ZhiGe1 , LI Yu2 , WANG YueBing2 , YOU XinZhao2, LONG Feng3(1 Key Laboratory of Earthquake Geodesy, Institute of Seismology, China Earthquake Administration, Wuhan 430071, China ;2 National Earthquake Infrastructure Service, Beijing 100036, China ;3 Sichuan Earthquake Administration, Chengdu 610041, Chin)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2018年第5期2122-2132,共11页
Chinese Journal of Geophysics
基金
中国地震局星火计划(XH17023Y)
国家自然科学基金(41704009
41704101)资助
