山东平原M_(S)5.5地震前岩石圈磁场异常变化及发震机理  

Abnormal Variation of Lithospheric Magnetic Field before the Pingyuan M_(S)5.5 Earthquake in Shandong Province and Its Seismogenic Mechanism

作　　者：张海洋 ZHANG Haiyang(Hebei Hongshan National Observatory on Thick Sediments and Seismic Hazards,Xingtai 054000,China;Baoding Earthquake Monitoring Center of Hebei Earthquake Agency,Baoding 071000,China)

机构地区：[1]河北红山巨厚沉积与地震灾害国家野外科学观测研究站,河北省邢台市054000 [2]河北省地震局保定地震监测中心站,河北省保定市071000

出　　处：《大地测量与地球动力学》2024年第9期892-898,904,共8页Journal of Geodesy and Geodynamics

基　　金：河北省地震科技星火计划(DZ2021121600003,DZ2024112200008,DZ20190422046)。

摘　　要：基于冀鲁交界地区2020~2023年连续4期的流动地磁观测资料,分析区域岩石圈磁场时空变化特征及其与2023-08-06山东平原M_(S)5.5地震的关系,并结合岩石磁学的实验室结果和断层亚失稳理论,探讨平原地震前的亚失稳特征及发震机理。结果表明:1)研究区岩石圈磁场时空变化特征在平原地震前有较为明显的异常反映,2020~2023年震中附近始终存在水平矢量的弱化区,并随着时间推移,出现水平矢量的弱化区逐渐向震中逼近的现象;震中附近始终存在地磁总强度、磁偏角、垂直分量的0值线。2)2020~2021年度震中附近各测点时序变化具有高度的一致性,较好地反映出测点附近断裂的协同化活动状态,或许可以作为识别断层进入亚失稳阶段的特征之一。3)分析应力与磁场强度的关系可知,林南断裂中东段、聊城-兰考断裂东北段地磁场总强度增大,地壳应力应处于释放状态;堂邑断裂、林南断裂西段地磁场总强度减小,地壳应力应处于积累状态。前者应力释放对后者的应力积累有促进作用,可能会导致后者的剪应力瞬时增加并超过其强度发生失稳,从而引发平原地震。Based on the mobile geomagnetic observation data of four consecutive periods from 2020 to 2023 in the border area of Hebei and Shandong,this paper analyzes the temporal and spatial variation characteristics of the regional lithospheric magnetic field and its relationship with the Pingyuan M_(S)5.5 earthquake on August 6,2023.Combined with the laboratory results of rock magnetism and the theory of fault meta-instability,it discusses the meta-instability characteristics before the plain earthquake and the seismogenic mechanism.The results show that:1)The spatial and temporal variation characteristics of the lithospheric magnetic field in the study area have obvious anomalies before the Pingyuan M_(S)5.5 earthquake.There is always a weakening area of the horizontal vector near the epicentre from 2020 to 2023,and with the passage of time,the weakening area with horizontal vector gradually approaches the epicentre;there is always a 0 value line of the total geomagnetic intensity,magnetic declination and vertical component near the epicentre.2)The time series variation of the observation points near the epicentre in 2020-2021 is highly consistent,which better reflects the synergistic activity state of the faults near the observation points,and may be used as one of the characteristics to identify the sub-instability stage of the faults.3)By analyzing the relationship between stress and magnetic field intensity,it can be seen that the total intensity of geomagnetic field in the middle and eastern segment of Linnan fault and the north-eastern segment of Liaocheng-Lankao fault increases,and the crustal stress should be in a release state;the total intensity of geomagnetic field in the western segment of Linnan fault and Tangyi fault decreases,and the crustal stress should be in an accumulation state.The stress release of the former can promote the stress accumulation of the latter,which may lead to the instantaneous increase of the shear stress of the latter and instability when it exceeds its strength,thus triggering the

关 键 词：平原M_(S)5.5地震 流动地磁 岩石圈磁场异常变化 亚失稳理论 发震机理 

分 类 号：P315[天文地球—地震学] P318[天文地球—固体地球物理学]