2020年西藏波密M4.4级震群序列特征和震源机制研究  

Study on Sequence Characteristics and Focal Mechanisim of Bomi M4.4 Earthquake Swarm in Tibet in 2020

作　　者：邹振轩 欧文东 益西拉姆 高锦瑞 张项 ZOU Zhenxuan;OU Wendong;YIXI Lamu;GAO Jinrui;ZHANG Xiang(Earthquake Agency of Tibet Autonomous Region,Lasa,Xizang,850000;Zhejiang Earthquake Agency,Hangzhou,Zhejiang,310013;Guangdong Earthquake Agency,Guangzhou,Guangdong,510000)

机构地区：[1]西藏自治区地震局,西藏拉萨850000 [2]浙江省地震局,浙江杭州310013 [3]广东省地震局,广东广州510000

出　　处：《浙江国土资源》2023年第S1期60-66,共7页Zhejiang Land & Resources

摘　　要：2020年6-8月,西藏区域地震台网共记录到发生在西藏波密地区的地震66次,其中M4.0以上地震9次,最大震级为M4.4。本文利用西藏区域地震台网记录的波形资料,对该震群进行了地震序列定位,用CAP波形反演方法,获得了震群中26个M≥3.0地震的震源机制解,对该区域发震构造与构造应力场进行了初步分析,结合卫星影像解析、水文气象、地质构造特征等方面进行了探讨,获得如下认识:(1)66次地震事件发生在上地壳浅部,呈带状分布,表明本次地震震群的发生与NW向色拉贡巴—汤目拉断裂构造有密切关系;(2)26个M≥3.0地震的多个震源机制表现出右旋走滑性质,与影像解译、地质调查结果一致;(3)易贡湖夏季气温升高,降雨和融雪导致径流量变大,造成局部应力变化,导致7-8月发生震群的概率高;综合分析认为,2020年西藏波密M4.4级震群的发生是地质、构造、水文气象因素等共同作用的结果,其中水是起到关键的诱发因素。From June to August 2020,the Tibet Regional Seismic Network recorded 66 earthquakes in Bomi area,Tibet,including 9 earthquakes above M4.0,with the maximum magnitude of M4.4.In this paper,the waveform data recorded by the Tibet regional seismic network are used to locate the earthquake sequence.The focal mechanism solutions of 26 earthquakes with M≥3.0 in the earthquake swarm are obtained by using CAP waveform inversion method.The geometric structure and stress field characteristics of seismogenic structures in this area are preliminarily analyzed.The main conclusions are as follows of(1)66 seismic events occurred in the shallow part of the upper crust and distributed in a zonal pattern,which indicates that the occurrence of this earthquake swarm is closely related to the NW trending seragongba-tangmula fault structure;(2)Multiple focal mechanisms of 26 earthquakes with M≥3.0 show dextral strike slip property,which is consistent with the results of image interpretation and geological survey;and(3)The temperature of Yigong Lake increases in summer,rainfall and snowmelt lead to the increase of runoff and the change of local stress,so the probability of earthquake swarm from July to August is high.Comprehensive analysis shows that the occurrence of Bomi M4.4 earthquake swarm in Tibet in 2020 is the result of geological,structural,hydro meteorological factors,among which water is the key inducing factor.66 seismic events occurred in the shallow part of the upper crust and distributed in a zonal pattern,which indicates that the occurrence of this earthquake swarm is closely related to the NW trending seragongba-tangmula fault structure.

关 键 词：波密震群 诱发地震 震源机制 断层构造 水文气象 

分 类 号：P315.33[天文地球—地震学]