2021年5月21日云南漾濞M6.4地震序列的矩心矩张量解及动力环境分析  

EARTHQUAKE CENTROID,SEISMIC MOMENT TENSOR AND DYNAMIC ENVIRONMENT ANALYSIS OF THE M_(S)6.4 EARTHQUAKE SEQUENCE IN YANGBI,YUNNAN ON MAY 21,2021

作　　者：郭祥云[1] 尹海权[2] 汪贞杰 杨辉[1] GUO Xiang-yun;YIN Hai-quan;WANG Zhen-jie;YANG Hui(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;The First Monitoring and Application Center,China Earthquake Administration,Tianjin 300180,China;Zhejiang Earthquake Agency,Hangzhou 310013,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局第一监测中心,天津300180 [3]浙江省地震局,杭州310013

出　　处：《地震地质》2021年第4期806-826,共21页Seismology and Geology

基　　金：国家重点研发计划项目(2017YFC1500501-04);中国地震局地球物理研究所基本科研业务专项(DQJB19A0115)共同资助。

摘　　要：文中利用中国地震台网中心汇编的震相数据,基于2021年5月18—28日云南漾濞地震周边101个地震台站的观测数据,采用双差定位方法对漾濞地震的前震-主震-余震序列进行了精定位研究,获得了2144个地震的精确位置。对结果进行分析后发现,此次地震的主余震分布、烈度等震线长轴方位与维西-乔后断裂的位置并不一致,且走向与其呈小角度相交,推断该地震的发震断裂可能是维西-乔后断裂的次级断裂或其他未知断裂。在精定位结果的基础上,采用贝叶斯自助优化BABO(Bayesian Bootstrap Optimisation)算法对2021年5月18—28日云南漾濞M 6.4地震和M≥3.6地震序列进行了矩张量反演,结果表明,云南漾濞地震序列具有明显的分段性。漾濞M 6.4主震为右旋走滑型兼有少量正倾分量,矩心深度为5.9km,大多数余震与主震的机制一致,以右旋走滑为主,只是在余震区的东南段西分支处震源性质有明显的不同,为正走滑型。整个地震序列的矩心深度为3.5~8.2km。应力场反演结果显示,震区主压应力场近SN向、走向滑动错动类型略带正倾分量。从地震序列分布和应力方向来看,本次地震的主要动力来源可能是川滇地块向SE的挤出作用,地震破裂过程和破裂样式代表了川滇地块挤出后的“松弛”过程。从构造背景上看,本次漾濞地震可能是在川滇地块向SE挤出和印度板块向W后撤(或者地幔底侵)2种动力环境下发生的。According to the Unified Earthquake Catalogue of China Earthquake Networks,using the seismic phase data compiled by the Seismic Data Center,the observations of 101 fixed and mobile seismic stations in the Yunnan region and its surrounding seismic network from May 18 to 28,2021,we conducted precise positioning research on the foreshock-mainshock-aftershock sequence of the Yangbi earthquake using the double-difference positioning method,and obtained the precise locations of 2144 earthquakes.It is found that the distribution of the main aftershocks and the long axis orientation of the intensity isoseismal are not consistent with the image position of the Weixi-Qiaohou Fault,and the strike intersects with a small angle.The seismogenic fault of this earthquake may be a secondary fault of the Weixi-Qiaohou Fault.On the basis of the precision positioning results,the Bayesian Bootstrap Optimization(BABO)algorithm is used to perform a moment tensor inversion on the M 6.4 earthquake and the M 3.6 and above earthquake sequences in Yangbi,Yunnan from May 18 to 28,2021.The results show that the sequence of Yangbi earthquake in Yunnan has obvious segmentation.The M 6.4 Yangbi main shock is of right-handed strike-slip type with a small amount of normal dipslip component,and the centroid depth is 5.9km.Most aftershocks have the same focal mechanism as the main shock,mainly right-handed strike-slip,except for the earthquakes in the west branch of the southeast section of the aftershock area,where the source property is obviously different,showing a normal strike-slip motion.The centroid depth of the entire earthquake sequence is 3.5~8.2km.The inversion results show that the principal compressive stress field of the earthquake area is in the near NS direction and the strike-slip dislocation is associated with a slight normal dipslip component.The spatial distribution of earthquakes shows that this earthquake sequence gradually developed from NW to SE,and the seismic density gradually dispersed from NW to SE.Therefore,it can be con

关 键 词：云南漾濞地震 维西-乔后断裂 地震精定位 应力场 矩张量解 

分 类 号：P315.2[天文地球—地震学]