基于GNSS和InSAR约束的2021年玛多M_(S)7.4地震同震滑动分布及应用  

Slip model of the 2021 M_(S)7.4 Madoi earthquake constrained by GNSS and InSAR coseismic deformation

作　　者：余鹏飞[1,2,3,4] 熊维 陈威[1,2,3] 乔学军 王迪晋[1,2,3] 刘刚 赵斌[1,2,3] 聂兆生 李瑜[4,5] 赵利江 张怀[1,2,3] YU PengFei;XIONG Wei;CHEN Wei;QIAO XueJun;WANG DiJin;LIU Gang;ZHAO Bin;NIE ZhaoSheng;LI Yu;ZHAO LiJiang;ZHANG Huai(Institute of Seismology,China Earthquake Administration,Wuhan 430071,China;Key Laboratory of Earthquake Geodesy,China Earthquake Administration,Wuhan 430071,China;Hubei Earthquake Administration,Wuhan 430071,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;China Earthquake Networks Center,Beijing 100045,China;Qinghai Institute of Basic Surveying and Mapping,Xining 810001,China)

机构地区：[1]中国地震局地震研究所,武汉430071 [2]中国地震局地震大地测量重点实验室,武汉430071 [3]湖北省地震局,武汉430071 [4]中国地震局地球物理研究所,北京100081 [5]中国地震台网中心,北京100045 [6]青海省基础测绘院,西宁810001

出　　处：《地球物理学报》2022年第2期509-522,共14页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41731071,41874018,42074015,42130101);地震科技星火计划(XH20038,XH21020)资助。

摘　　要：2021年5月22日青海省果洛藏族自治州玛多县发生M_(S)7.4地震,震中位于青藏高原中部的巴颜喀拉块体,这是近20多年来在巴颜喀拉块体周边发生8次M≥7级强震后,块体内部的一次强震,也是汶川地震以来中国大陆发生的最大一次地震,因此该地震的成因及周边地区未来的地震危险性值得重点关注.本文利用震后及时获取的39个近场流动GNSS观测,联合61个GNSS连续观测、Sentinel-1和ALOS-2 InSAR观测获取了本次地震精细的同震形变场,以此为约束,基于均匀弹性半无限位错模型,反演了发震断层的滑动分布,并计算了同震库仑应力变化.GNSS水平同震形变十分显著,断层南北两侧的GNSS点位,最大水平形变分别达0.7 m和-1.2 m,距震中200 km的测点仍有1 cm左右的同震形变.Sentinel-1和ALOS-2的升降轨InSAR同震形变场显示此次地震造成了约160 km长的地表破裂,最大视线向形变分别达0.9 m和1.2 m.同震滑动分布模型显示,发震断层由主段和次段组成,长度分别为170 km和20 km,主段倾向北,倾角85°,平均滑动角为-4.36°,表明玛多地震是一次典型的走滑型地震.次段倾向南,倾角68°,平均滑动角为-11.84°.地震破裂主要集中在0~15 km深度范围,最大滑动量为4.4 m,对应深度6.97 km.反演给出的矩震量为1.61×10^(20)N·m,对应矩震级M_(W)7.4.主发震断层上存在4个凹凸体,玛多地震是一次不对称双侧破裂事件.结合余震精定位、野外调查及地质资料,我们认为主发震断裂为昆仑山口—江错断裂,东部的次级破裂与主破裂机制不同.同震库仑应力结果显示,东昆仑断裂玛沁段应力有所增加(>0.01 MPa),处于应力加载状态,未来发生强震的危险性较高.On May 22,2021,an M_(S)7.4 earthquake occurred in Madoi county,Guoluo Tibetan Autonomous Prefecture,Qinghai Province of China.The epicenter was located in the Bayan Har block in the middle of the Tibetan Plateau.It was another strong earthquake occurred in the Bayan Har block after eight M≥7 earthquakes occurred around the boundaries of the block in recent 20 years.It is also the largest earthquake in China since the 2008 Wenchuan earthquake.Therefore,the cause of the earthquake and the regional seismic risk deserve special attention.The near-field campaign GNSS observations,combined with continuous GNSS observations,Sentinel-1,and ALOS-2 InSAR observations were used to obtain the fine coseismic deformation field of the Madoi earthquake.The horizontal deformation field derived from GNSS was remarkable.The maximum horizontal displacements of GNSS stations located on both sides of the fault are 0.7 m and-1.2 m,respectively.The deformation was remains 1 cm even at a large distance of 200 km from the epicenter.The InSAR coseismic deformation field of Sentinel-1 and ALOS-2 shows that the earthquake caused a surface rupture of about 160 km long,with the maximum line-of-sight(LOS)deformation of 0.9 m and 1.2 m respectively.Based on the coseismic deformation field derived from GNSS and InSAR interferograms,we inverted for the slip distribution.The result showed that the seismogenic fault consists of a main segment and a secondary segment with the length of 170 km and 20 km,respectively.The main segment dips to the north,and its dip angle is 85°.The average rake angle was-4.36°,indicating that the Madoi earthquake was dominated by a left-lateral strike-slip.The dip direction of the secondary segment is opposite to that of the main,with a dip angle of 68°,and the average rake angle was-11.84°.The coseismic slip is concentrated at a depth of 0~15 km.The maximum slip was 4.4 m,at a depth of 6.97 km.The estimated total seismic moment is 1.61×10^(20) N·m,corresponding to a magnitude of M_(W)7.4.There are 4 asperities r

关 键 词：2021玛多地震 GNSS INSAR 同震形变 滑动分布 

分 类 号：P223[天文地球—大地测量学与测量工程] P313[天文地球—测绘科学与技术]