2021年四川泸县M 6.0地震发震机理及地震活动时空演化特征  

Seismogenic mechanism of the 2021 M 6.0 Luxian earthquake and seismicity spatio-temporal characteristics around the source region

作　　者：李欣蔚 张广伟 谢卓娟 李世杰 吕悦军 LI XinWei;ZHANG GuangWei;XIE ZhuoJuan;LI ShiJie;Lü YueJun(National Institute of Natural Hazards,Ministry of Emergency Management of China,Beijing 100085,China;Key Laboratory of Compound and Chained Natural Hazards Dynamics,Ministry of Emergency Management of China,Beijing 100085,China;Guizhou Earthquake Disaster Risk Prevention and Governance Center,Guiyang 550001,China)

机构地区：[1]应急管理部国家自然灾害防治研究院,北京100085 [2]复合链生自然灾害动力学应急管理部重点实验室,北京100085 [3]贵州省震灾风险防治中心,贵阳550001

出　　处：《地球物理学报》2022年第11期4284-4298,共15页Chinese Journal of Geophysics

基　　金：中央级公益性科研院所基本科研业务专项(ZDJ2020-09)资助.

摘　　要：2021年9月16日四川泸县发生M 6.0地震,该地震发震构造不明,发震机理尚存在争议.地震精定位和震源机制有助于分析地震活动时空演化与震源破裂特征,能够有效揭示活动构造机制和地震发生机理,为评估区域地震危险性提供科学依据.为此,本文首先采用双差定位法对震中及附近2009年1月至2021年10月发生的地震进行了精定位,结果显示,研究区地震震源深度大多集中在10 km范围内,事件主要沿地表断层呈条带状或丛集分布,部分震群邻近当地工业井,周边无明显断层分布.其次,通过CAP波形反演计算得到M≥3.5地震的震源机制解,表明研究区震源破裂以逆冲挤压型为主,部分震源机制解具有不确定性.基于震源机制解反演区域应力场,进一步探讨了区域应力场与地震事件的力学一致性.研究结果显示,区域应力场以水平构造挤压作用为主,部分事件震源机制解与其吻合度较低,暗示存在局部应力差异.综合地震活动时空演化特征、已知断层展布以及区域应力场等研究结果,认为华蓥山断裂带南段的地震活动与资源开采活动密切相关,泸县M 6.0地震是在局部应力场扰动下,下方滑脱层活动触发了上覆隐伏断层的挤压错动而产生.An M 6.0 earthquake occurred in the Luxian County,Sichuan Province on September 16,2021,drawing much attention to its mechanism of earthquake generation.The earthquake relocation and focal mechanism are useful for analyzing the spatial-temporal evolution of seismic activity and the characteristics of source rupture,which can give new insight into the seismogenic structure and mechanism and provide a scientific basis for the region seismic risk assessment.In this paper,we firstly relocate the earthquake sequences in the study region from January 2009 to October 2021 with the double-difference method.The results show that the source depths are mainly distributed above 10 km depth,and the earthquakes generally occur along the surface traces of preexisting faults.However,events showing cluster characteristics are adjacent to the local industrial wells that no faults are observed.Secondly,we invert the focal mechanisms of the M≥3.5 earthquakes using the CAP waveform inversion method,and the results show that the source rupture is dominated by a reverse-fault type.Meanwhile,some of the focal mechanism solutions are characterized by an unknown type.Based on the focal mechanism solutions,we obtain the regional stress field and further investigate the mechanical consistency between the regional stress field and the seismic events.Our results point out that the stress regime exhibit a significant local change.Combining the spatial and temporal patterns of earthquake distribution,we conclude that the seismic activity in the southern part of the Huayingshan fault is closely related to the resource extraction activities,and the 2021 M 6.0 Luxian earthquake is associated with the extrusional dislocation of an unmapped fault overlying a detachment layer.

关 键 词：泸县M 6.0地震 华蓥山断裂 双差定位 发震机理 震源机制解 

分 类 号：P315[天文地球—地震学]