2022年四川芦山M_(S)6.1地震前应力状态研究  

Study on the Stress State before the 2022,Lushan,Sichuan M_(S)6.1 Earthquake

作　　者：张致伟[1,2] 曾宪伟 王迪[1] 路茜 王玮铭[1] 杨鹏 龙锋 ZHANG Zhiwei;ZENG Xianwei;WANG Di;LU Qian;WANG Weiming;YANG Peng;LONG Feng(Sichuan Earthquake Agency,Chengdu 610041,Sichuan,China;College of Geophysics,Chengdu University of Technology,Chengdu 610059,Sichuan,China;Earthquake Agency of Ningxia Hui Autonomous Region,Yinchuan 750001,Ningxia,China)

机构地区：[1]四川省地震局,四川成都610041 [2]成都理工大学,四川成都610059 [3]宁夏回族自治区地震局,宁夏银川750001

出　　处：《地震研究》2024年第4期483-492,共10页Journal of Seismological Research

基　　金：国家重点研发计划专题(2021YFC3000705-07);国家自然科学基金地震科学联合基金(U2139203);中国地震局“大震短临跟踪技术研究团队”项目;四川省地震局“防震减灾公共服务平台建设创新团队”项目.

摘　　要：为研究2022年6月1日四川芦山M_(S)6.1地震的孕育和发生过程,采用CAP方法反演了2013年芦山M_(S)7.0主震及M_(S)≥5.0余震的震源机制解,并基于应力张量方差与b值时空分布特征,探讨了芦山M_(S)6.1地震的力学机制和震源区的应力状态。结果表明:2022年芦山M_(S)6.1地震震源机制表现出与2013年芦山M_(S)7.0主震和5级余震相似的逆冲型破裂特征,压应力轴方位与龙门山断裂带南段区域应力场一致。2013年芦山M_(S)7.0地震后震中及附近的应力张量方差和b值长期处于低值状态,2022年芦山M_(S)6.1地震前震中及附近出现了应力张量方差和b值的低值异常,表明芦山余震区处于较高的应力水平。分析认为:巴颜喀拉块体持续东向运动受到华南块体的阻挡,震中所在区域长期受挤压逆冲作用,从而使芦山余震区长期处于应力积累的状态,芦山M_(S)6.1地震也是在这种动力学背景下发生的。On June 1,2022,an M_(S)6.1 earthquake struck Lushan Country,Ya'an City of Sichuan Province.The earthquake is another significant event that occurred in the aftershock zone of the Lushan M_(S)7.0 earthquake on May 20,2013.To figure out the genesis and occurrence of the Lushan M_(S)6.1 earthquake,the CAP inversion method is used to calculate the focal mechanism of the Lushan M_(S)7.0 mainshock and its M_(S)≥5.0 aftershocks.And the mechanical mechanism and the stress state in the source area before the Lushan M_(S)6.1 earthquake are discussed based on the spatial and temporal distribution of the stress tensor variance and b value.The main insights are as follows:The focal mechanism of the Lushan M_(S)6.1 earthquake is featured as a thrust rupture,which is similar to the feature of the focal mechanism of the Lushan M_(S)7.0 earthquake and its M_(S)≥5.0 aftershocks.The direction of the principal compressive stress is consistent with the regional stress field of the southern section of the Longmenshan fault zone.The stress tensor variance and b value around the epicenter of the Lushan M_(S)7.0 earthquake are in a low state in a long period.What is more,shortly before the Lushan M_(S)6.1 earthquake,in its focal area there appeared low-value anomalies of the stress tensor variance and b value,indicating that the Lushan M_(S)7.0 earthquake aftershock zone had been keeping a higher stress level.The continuous eastward movement of the Bayan Har block is blocked by the South China block.Thus,the aftershock zone of the Lushan M_(S)7.0 earthquake is under the action of the horizontal extrusion and thrust,which leads to the long-term stress accumulation in this zone.Hence in this dynamic background,the Lushan M_(S)6.1 earthquake occurred.

关 键 词：芦山M_(S)6.1地震 芦山M_(S)7.0地震 震源机制解 应力张量方差 B值 应力状态 

分 类 号：P315.72[天文地球—地震学]