2022年四川泸定M_(S)6.8地震余震序列的自动构建与地震活动性分析  

Auto-building of aftershock sequence and seismicity analysis for the 2022 Luding,Sichuan,M_(S)6.8 earthquake

作　　者：刘泽民 李俊 苏金蓉[2] 于子叶 黄春梅[2] 祁玉萍[2] 陈依伲 王伟涛[1,4] LIU ZeMin;LI Jun;SU JinRong;YU ZiYe;HUANG ChunMei;QI YuPing;CHEN YiNi;WANG WeiTao(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Sichuan Earthquake Agency,Chengdu 610041,China;Zhejiang Earthquake Agency,Hangzhou 310013,China;Key Laboratory of Earthquake Source Physics,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 [2]四川省地震局,成都610041 [3]浙江省地震局,杭州310013 [4]中国地震局震源物理重点实验室,北京100081

出　　处：《地球物理学报》2023年第5期1976-1990,共15页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(42074060);中国地震局地球物理研究所基本业务专项(DQJB19B29);地震科技星火计划项目(XH211103和XH212301Y)资助。

摘　　要：北京时间2022年9月5日12时52分,四川甘孜州泸定县发生M_(S)6.8地震(以下简称泸定地震).本文基于神经网络方法从泸定地震周边200 km之内57个台站2022年9月5—15日的连续波形资料中拾取Pg/Sg震相到时,对由优选的震相识别阈值筛选后的震相到时进行震相关联和定位分析,经上述处理流程获得自动检测目录(AUTO)包含10590个地震事件,为同期台网人工目录(即中国地震台网中心目录,CENC)数量的3.3倍,完备性震级由ML1.0下降至ML0.5.基于波形互相关的双差定位方法获得的8279个地震的时空分布特征表明,2022年泸定M_(S)6.8地震的主震及余震主要发生在鲜水河断裂磨西段,沿着该断裂在NNW-SSE方向分布并表现出明显分段特征,北段总体深度较浅,深度集中在10 km以上,中段和南段相对较深,深度分布在5~20 km之间.此外,余震序列在鲜水河断裂上展现出高倾角的特征,而在主震SW方向的海螺沟断裂附近与鲜水河断裂呈共轭展布,推测在中段海螺沟附近有一条走向SW、倾向SE的低倾角分支断裂.研究结果表明,利用人工智能方法快速实现中强地震余震序列的自动化检测是获取地震发震构造、破裂方向等信息的有效方法.At 12∶52 Beijing Time on September 5,2022,an M_(S)6.8 earthquake struck Luding County,Garze Prefecture,Sichuan Province,China(hereafter referred to as Luding earthquake).Based on the continuous waveforms collected between September 5 and September 15,2022 from 57 stations located within 200 km around the mainshock,we pick Pg/Sg phases using the neural network method and screen them through the optimal threshold.After phase association and earthquake location,we obtain the automatic detected catalogue(AUTO)with 10590 events,about 3.3 times the number of the manual catalogue,built by China Earthquake Network Center(CENC),in the same study period.The magnitude of completeness(MC)also decreases from ML1.0 to ML0.5.Then we relocate the events with a cross-correlation-based double-difference location method(HypoDD),and obtain 8279 earthquakes.Our relocation results show that the mainshock and aftershocks of Luding earthquake mainly occurred on the NNW-SSE direction along the western Moxi section of the Xianshuihe Fault and also show an obvious sectional characteristics with depths of 0~10 km for the northern section and depths of 5~20 km for the middle and southern sections.Additionally,the aftershocks distribution shows a high dip angle along the Xianshuihe Fault,while there is a cluster of aftershocks in the southwestern direction of the mainshock along the Hailuogou Fault,which is conjugated with Xianshuihe Fault.We infer that a low-dip-angle fault with strike of SW and dip direction of SE may exist near the Hailuogou Fault of the middle section.Our results demonstrate the machine learning based aftershock identification is a rapid and effective method for better understanding of seismogenic structure and rupture direction.

关 键 词：泸定地震 神经网络 余震序列 地震精定位 

分 类 号：P315[天文地球—地震学]