2021年云南漾濞M_(S)6.4地震震区断裂构造特征  

Fault Structure Characteristics of the Yangbi,Yunnan M_(S)6.4 Earthquake in 2021

作　　者：刘昌伟 常祖峰[1] 王光明 李鉴林 LIU Changwei;CHANG Zufeng;WANG Guangming;LI Jianlin(Yunnan Earthquake Agency,Kunming 650224,Yunnan,China)

机构地区：[1]云南省地震局,云南昆明650224

出　　处：《地震研究》2023年第3期323-331,共9页Journal of Seismological Research

基　　金：云南省地震局自立科研项目(2022K02);云南省第一次全国自然灾害风险普查项目.

摘　　要：为进一步查明震区断裂构造特征,摸清其风险底数,基于云南省地震灾害风险普查漾濞县1∶25万地震构造填图任务,对漾濞县行政区内多条断裂构造开展野外调查。结果表明:①结合震区新生代以来的构造演化开展分析,认为草坪断裂在维西—乔后断裂开始活动之前便已经形成,在地震破裂发生时此类先存断裂对区域应力释放具有十分重要的作用;②草坪断裂为一条早第四纪断裂,第四纪以来活动并不显著,不具备独立发生M_(S)≥6.0强震的构造条件;③在维西—乔后断裂中段全新世以来持续强烈的活动构造背景下,漾濞M_(S)6.4地震为一次沿先存断裂构造面发生破裂的地震事件;④地震精定位结果显示,地震序列SE端存在分叉的几何特征,认为地震产生的右旋剪切作用使得后期余震破裂继承了腊时断裂、小庄村断裂及罗家村断裂的几何构造面,并分散、吸收了剩余应力。An M_(S)6.4 earthquake occurred near Yangbi County,Bai Autonomous Prefecture of Dali,Yunnan Province on May 21,2021.The earthquake location is characterized by complex geological structures,and the epicenter is located in the Weixi-Qiaohou fault at the west edge of the Sichuan-Yunnan rhombic block.In order to investigate the risk of earthquake disasters and identify the characteristics of the fault structures in the region,a field survey was carried out on several fault structures,based on the 1∶250000 seismic structure mapping of Yangbi County.The results show that the Caoping fault has no significant activity since the Quaternary,and it does not have the tectonic conditions for above M_(S)6.0 strong earthquakes independently;The regional tectonic evolution indicates that the Caoping fault was formed before the the Weixi-Qiaohou fault started to act,such a preexisting fault and the likes play an important role in regional stress release in the earthquake event.Under the condition of intense Holocene activity in the middle section of the Weixi-Qiaohou fault,the Yangbi M_(S)6.4 earthquake was an event that ruptured along the tectonic plane of the preexisting fault.Relocation results show that the SE end of the seismic sequence has a geometric feature of bifurcation.We believe that the dextral shearing caused by the earthquake makes the later aftershock rupture inherit the geometric structure of the Lashi fault,the Xiaozhuang village fault and the Luojia village fault,and disperses and absorbs the residual stress.

关 键 词：漾濞M_(S)6.4地震 地震灾害风险普查 草坪断裂 发震构造 

分 类 号：P315.22[天文地球—地震学]