2022年青海门源6.9级地震前岩石圈磁场异常变化分析  

Variation of lithospheric magnetic field anomalies before the Menyuan,Qinghai M_(S)6.9 earthquake in 2022

作　　者：张海洋 苏树朋 赵慧琴[1,2] ZHANG Haiyang;SU Shupeng;ZHAO Huiqin(Hebei Hongshan National Observatory on Thick Sediments and Seismic Hazards, Xingtai 054000, Hebei, China;Baoding Earthquake Monitoring Center Station, Hebei Earthquake Agency, Baoding 071000, Hebei, 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,河北邢台054000 [2]河北省地震局保定地震监测中心站,河北保定071000

出　　处：《地震工程学报》2022年第3期735-743,共9页China Earthquake Engineering Journal

基　　金：河北省地震科技星火计划重点项目(DZ20190422046);河北省地震科技星火计划青年项目(DZ202108090029)。

摘　　要：基于青海及甘肃部分地区2020—2021年2期流动地磁测点的观测资料,获得该地区的岩石圈磁场异常变化,通过研究岩石圈磁场各个分量的变化特征,系统分析2022年1月8日青海门源6.9级地震前岩石圈磁场的异常变化特征。结果表明:(1)门源地震前,震中区域岩石圈磁场各个分量具有较为明显的异常显示。具体表现为:震中区域附近岩石圈磁场变化的水平矢量具有方向转向及幅值弱化的异常变化现象;垂直矢量方向出现明显的南向、北向对冲的异常现象;磁偏角在震中附近具有“0”变线和高梯级带分布;总强度和垂直分量在震中附近具有“0”变线分布,并发生弯曲。(2)依据压磁效应分析,冷龙岭断裂北部岩石圈磁场增大,应力变化主要以释放为主,应力变化应处于较低水平;冷龙岭断裂南部岩石圈磁场强度减小,应力变化主要以积累为主,应力变化应处于较高水平。门源地震前,冷龙岭断裂构造应力调整引起的压磁效应可能是造成震中区域岩石圈磁场异常变化的主要原因。Based on the observation data of mobile geomagnetic survey points in some areas of Qinghai and Gansu from 2020 to 2021,the abnormal changes of lithospheric magnetic field in the study area were obtained,and the anomalies characteristics of lithospheric magnetic field before the Menyuan,Qinghai M_(S)6.9 earthquake on January 8,2022 were systematically analyzed.The results show that:(1)Before the Menyuan earthquake,each component of the lithospheric magnetic field in the epicentral area showed obvious anomalies.The horizontal vector of the lithospheric magnetic field showed abnormal change of direction turning and amplitude weakening near the epicenter;the vertical vector direction showed obvious anomaly of south-north offset.In addition,the magnetic declination had a zero-variation line near the epicenter,showing a high gradient belt distribution.The total intensity and vertical component had a zero-variation line distribution and bending near the epicenter.(2)According to the piezomagnetic effect,the lithosphere magnetic field in the north of Lenglongling fault increased,and the stress mainly released at a low level.The lithosphere magnetic field in the south of Lenglongling fault decreased,and the stress mainly accumulated at a high level.Before the Menyuan earthquake,the piezomagnetic effect caused by the tectonic stress adjustment of Lenglongling fault might be the main reason for the abnormal variation of lithosphere magnetic field in the epicentral region.

关 键 词：门源6.9级地震 流动地磁 岩石圈磁场 压磁效应 

分 类 号：P319.56[天文地球—固体地球物理学]