2022年四川泸定M_(S)6.8地震震源基本特征  

Primary source characteristics of the 2022 Sichuan Luding M_(S)6.8 Earthquake

作　　者：张喆 房立华[1] 许力生[1] ZHANG Zhe;FANG LiHua;XU LiSheng(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学报》2023年第4期1397-1408,共12页Chinese Journal of Geophysics

基　　金：国家自然科学基金(42104043);中国地震局地球物理研究所基本科研业务费(DQJB22R35);地震联合基金(U2039208)联合资助。

摘　　要：2022年9月5日,在四川省甘孜州泸定县发生M_(S)6.8地震.本研究收集区域台网震相数据、全球地震台网(GSN)、国际数字地震台网联盟(FDSN)与德国地学中心GEOFON台网的宽频带P波数据,利用双差定位、矩心矩张量解反演、有限断层波形反演和视震源时间函数分析等方法,分析了此次地震震源的基本特征.重定位结果显示,余震分布具有丛集性,3个地震丛分别集中在震中附近以及相距30 km左右的东南端和西北端,总体上西北端地震较浅,东南端地震较深.矩心矩张量反演表明,矩心位于29.55°N,102.14°E,深度16 km,释放地震矩1.0068×10^(19)N·m,相当于矩震级MW6.60,双力偶成分占88%,是一次近纯走滑的地震事件.结合余震分布可以断定,地震发生在走向163°、倾角77°(倾向西南),滑动角为-5°的断层面.有限断层反演显示,破裂区主要由两部分构成,破裂起始点及其周围是主要破裂区;另一破裂区位于其东南,总体表现为从西北向东南的单侧破裂,最大滑动量约1.4 m,位于起始破裂点附近.从矩心矩张量反演和有限断层反演得到的震源时间函数均表明,地震持续时间约20 s,能量释放分两个阶段.根据视震源时间函数的方位依赖性推断,破裂优势方向在165°方位,与断层走向一致,由平均视震源时间函数估计的标量地震矩几乎与有限断层反演得到的完全一致,且与矩心矩张量反演结果非常接近.An M_(S)6.8 earthquake struck Luding,a county in Sichuan Province on September 5,2022.We collected the phase data of the regional seismograph network,the seismic broadband P-waveform data from the Global Seismic Network(GSN),the Federal Digital Seismic Networks(FDSN)and the GEOFON Network of the German Research Centre for Geosciences,and quickly analyzed the primary source characteristics of this earthquake by using techniques of the double-difference relocation,the centroid moment tensor inversion,the finite-fault waveform inversion,and the apparent source time function(ASTF)analysis.From the relocation,the aftershocks were distributed in style of swarms.Three swarms were clustered around the epicenter,and about 30 km northwestern and southeastern,respectively.Generally,the events in northwest were shallower than those in southeast.The centroid moment tensor inversion indicated that the centroid was at 29.55°N,102.14°E and at depth of 16 km,a scalar moment of 1.0068×10^(19)N·m was released,yielding a magnitude of MW6.60,the double-couple component was 88%,and it was an approximately pure strike-slip event.Considering the spatial feature of the aftershock distribution,we concluded that this event occurred on a fault plane of strike 163°,dip 77°(dipping to southwest),rake-5°.The finite-fault inversion showed that the rupture area was composed of two patches,with one around the initial point,which is the main part,whereas the other being more southeastern,and generally the rupture appeared to be unilateral from northwest to southeast,with a maximum slip of 1.4 m near the initial point.As the centroid moment tensor inversion and the finite-fault inversion showed,the whole duration time was about 20 s,and clearly,the energy was released in two periods.Deduced from the azimuthal dependence of the ASTFs,the predominant rupture direction was in azimuth of~165°,which is consistent with the faulting strike,and the estimate of scalar seismic moment based on the averaged ASTF was almost identical with what was solve

关 键 词：四川泸定M_(S)6.8地震 双差定位 矩心矩张量反演 有限断层反演 时空破裂过程 

分 类 号：P315[天文地球—地震学]