Seismogenic model of the 2023 M_(W)5.5 Pingyuan earthquake in North China Plain and its tectonic implications  

作　　者：Shiguang Wang Libo Han Junju Xie Liping Fan Xiang Huang Jinmeng Bi Hongfeng Yang Lihua Fang 

机构地区：[1]Institute of Geophysics,China Earthquake Administration,Beijing 10081,China [2]Tianjin Earthquake Agency,Tianjin 300201,China [3]Earth System Science Programme,The Chinese University of Hong Kong,Shatin,Hong Kong 999077,China [4]Beijing Baijiatuan Earth Science National Observation and Research Station,Beijing 100095,China

出　　处：《Earthquake Science》2024年第6期499-513,共15页地震学报（英文版）

基　　金：supported from the National Natural Science Foundation of China(No.42374081);the Fundamental Research Funds for the Institute of Geophysics,China Earthquake Administration(Nos.DQJB23B22,DQJB22K36 and DQJB23Z04);Hong Research Grants Council(Nos.14306122 and 14308523)。

摘　　要：The 6 August 2023 M_(W)5.5 Pingyuan earthquake is the largest earthquake in the central North China Plain(NCP)over the past two decades.Due to the thick sedimentary cover,no corresponding active faults have been reported yet in the epicenter area.Thus,this earthquake presents a unique opportunity to delve into the buried active faults beneath the NCP.By integrating strong ground motion records,high-precision aftershock sequence relocation,and focal mechanism solutions,we gain insights into the seismotectonics of the Pingyuan earthquake.The aftershocks are clustered at depths ranging from 15 to 20 km and delineate a NE-SW trend,consistent with the distribution of ground motion records.A NE-SW nodal plane(226°)of the focal mechanism solutions is also derived from regional waveform inversion,suggesting that the mainshock was dominated by strike-slip motion with minor normal faulting component.Integrating regional geological data,we propose that an unrecognized fault between the NE-SW trending Gaotang and Lingxian-Yangxin faults is the seismogenic fault of this event.Based on the S-wave velocity structure beneath the NCP,this fault probably extends into the lower crust with a high angle.Considering the tectonic regime and stress state,we speculate that the interplay of shear strain between the Amurian and South China blocks and the hot upwelling magma from the subducted paleo Pacific flat slab significantly contributed to the generation of the Pingyuan earthquake.

关 键 词：Pingyuan earthquake aftershock relocation focal mechanism S-wave velocity structure North China Plain 

分 类 号：P315.2[天文地球—地震学]