文章摘要

文章信息/Info

Title:: Relocation of the 2021 Yangbi,Yunnan M_S6.4 Earthquake Sequence and Discussion of Its Seismogenic Fault

Author(s):: JIANG Jinzhong; FU Hong; LI Tao; (Yunnan Earthquake Agency,Kunming 650224,Yunnan,China)

Keywords:: the 2021 Yangbi M_S6.4 earthquake; the double-difference relocation; the cross-correlation analysis; focal mechanism solution; seismogenic fault

摘要:: 利用云南地震台网提供的地震编目快报观测报告和地震事件波形数据,采用联合波形互相关分析的双差地震定位方法,对2021年5月21日云南漾濞M_S6.4地震前3天至震后2天期间发生的地震事件进行了重定位,并基于两种不同的区域速度模型,采用CAP方法反演了序列中3次M_S≥ 5.0地震的震源机制解和矩心深度。结果表明:双差重定位获得了漾濞地震序列中1 012次地震的精确位置,水平和垂直方向的定位误差分别为1.1 km和3.0 km。3次M_S≥5.0地震的震源机制解和深度均有所不同,初步分析认为这可能是由断裂深浅部的结构、形态差异或地震破裂后震源区附近的应力调整或流体运移导致的断层成核破裂变化所致。综合地震重定位、震源机制解反演及区域活动构造资料,初步分析认为漾濞M_S6.4地震的发震破裂面走向约为140°,倾角约为80°,滑动角约为-160°,发震断层可能为维西—乔后断裂中段的一条或多条次级断裂,且具有右旋走滑特征。

Abstract:: Using earthquake catalog and seismic waveforms data recorded by the Yunnan Seismic Network,we relocate the Yangbi,Yunnan M_S6.4 earthquake sequence occurring from 18th to 23th May,2021 through the double-difference relocation algorithm and the cross-correlation analysis.We also invert the focal mechanisms and depths of the three M_S≥5.0 events(including the mainshock)in the Yangbi earthquake sequence with the cut-and-paste(CAP)method.Then we obtain epicenters and focal depths of 1 012 events,with median relocation errors about 1.1 km and 3.0 km in horizontal and depth direction,respectively.The focal mechanisms and the depths of each of the three events inverted are slightly different,which could be attributed to the different fault structures between the shallow and the deep part of the seismogenic fault zone,or the stress adjustment or fluid migration after the mainshock.According to the double-difference relocation,CAP inversions and distribution of regional geological structures,we preliminary infer that the Weixi-Qiaohou Fault could be the seismogenic fault of the 2021 Yangbi M_S6.4 earthquake sequence.The parameters of the Fault's fracture surface,strike/dip/slip,could be 140°/80°/-160°.