2021年5月21日云南漾濞M_(S)6.4地震:一次破裂在隐伏断层上的浅源走滑事件  

The 21 May 2021 M_(S)6.4 Yangbi(Yunnan)earthquake:A shallow strike-slip event rupturing in a blind fault

作　　者：杨九元 温扬茂[1,2] 许才军 YANG JiuYuan;WEN YangMao;XU CaiJun(School of Geodesy and Geomatics,Wuhan University,Wuhan 430079,China;Key Laboratory of Geospace Environment and Geodesy,Ministry of Education,Wuhan 430079,China;Key Laboratory of Geophysical Geodesy,Ministry of Natural Resources,Wuhan 430079,China)

机构地区：[1]武汉大学测绘学院,武汉430079 [2]地球空间环境与大地测量教育部重点实验室,武汉430079 [3]自然资源部地球物理大地测量重点实验室,武汉430079

出　　处：《地球物理学报》2021年第9期3101-3110,共10页Chinese Journal of Geophysics

基　　金：国家重点研发计划(2018YFC1503604,2019YFC1509204);国家自然科学基金(41721003,41974004)资助.

摘　　要：2021年5月21日,在中国云南省大理州漾濞县发生了M_(S)6.4地震.该地震震中位于川滇菱形块体西部边缘的维西—乔后—巍山断裂附近.作为该区域过去45年以来发生的最大地震,快速的灾害反应及震源参数反演将为防震减灾提供重要的帮助.由于未搜集到与此次地震地表破裂相关的报告,这次地震的发震断层目前仍难以确定.本文利用哨兵1A/B卫星的合成孔径雷达干涉(InSAR)数据获得了与此次地震相关的同震形变,并反演了这次事件的断层几何参数及详细的滑动分布.反演结果显示:破裂断层以右旋走滑运动为主,兼有少量的正断分量;滑动主要分布在2到12 km深度范围内,在约7 km深度处滑动达到最大,约为0.64 m.破裂断层浅部0到2 km范围内滑动的缺失揭示了一个重要的滑动亏损区,该区域很可能被震后余滑及震间浅部滑动所弥补.通过对反演结果、余震序列和局部断层构造特性的综合分析,认为此次地震可能破裂在维西—乔后—巍山断裂的隐伏分支断层或一个独立的未知的隐伏主断层上.计算的同震库仑应力变化表明维西—乔后—巍山断裂的巍山盆地段北端、维西—乔后—巍山断裂的玉狮场—乔后段最南端及洱源—弥渡断裂的中段北端具有较高的破裂风险.On 21 May 2021,an M_(S)6.4 earthquake struck the Yangbi County,Dali Prefecture,Yunnan Province,China.The epicenter of this earthquake is located near the Weixi-Qiaohou-Weishan fault on the western edge of the Sichuan-Yunnan rhombus block.As the largest earthquake to hit this area in the past 45 years,rapid disaster response and source parameters inversion will provide important help for earthquake disaster mitigation.Because no surface rupture related to this event has been reported,the seismogenic fault of this earthquake is still unknown.In this study,we acquired coseismic deformation related to this earthquake by means of Sentinel-1A/B interferometric synthetic aperture radar(InSAR)data and then inverted the fault geometry and detailed slip distribution.The inversion results show that the coseismic rupture is mainly dominated by the right-lateral strike-slip faulting with minor normal components.The majority of slip is confined at depths from 2 to 12 km with a peak value of 0.64 m at depth of 7 km.The absence of slip in the shallow part(0~2 km)of the rupture fault reveals an important coseismic slip deficit area,which is likely to be compensated by postseismic afterslip and interseismic slip.By an integrated analysis of the inversions,aftershock sequence and tectonic feature of the regional faults,we proposed that a blind branch fault splaying from the Weixi-Qiaohou-Weishan fault at depth or a new unknown blind fault may be responsible for this earthquake.Our calculated coseismic Coulomb stress changes show a high rupture risk at the northern extremity of the Weishan segment of the Weixi-Qiaohou-Weishan fault,southernmost end of the Yushichang-Qiaohou segment of the Weixi-Qiaohou-Weishan fault and northern extremity of the middle segment of the Eryuan-Midu fault.

关 键 词：川滇菱形块体 漾濞地震 隐伏断层 合成孔径雷达干涉测量 大地测量反演 

分 类 号：P315[天文地球—地震学] P228[天文地球—固体地球物理学]