2021年5月22日青海玛多M_(S)7.4地震前地磁加卸载响应比变化特征  

Analysis on characteristics of geomagnetic load-unload response ratio method before Maduo M_(S)7.4 earthquake

作　　者：李霞[1] 冯丽丽[1] 赵玉红[1] 刘磊[1] 苟智栋[1] 戴苗 LI Xia;FENG LiLi;ZHAO YuHong;LIU Lei;GOU ZhiDong;DAI Miao(Qinghai Earthquake Agency,Xining 810001,China;Hubei Earthquake Agency,Wuhan 430071,China)

机构地区：[1]青海省地震局,西宁810001 [2]湖北省地震局,武汉430071

出　　处：《地球物理学进展》2022年第3期964-970,共7页Progress in Geophysics

基　　金：中国地震局科技星火计划“南北地震带地磁垂直强度极化分频特征研究”(XH21037Y);中国地震局震情跟踪定向工作任务“地磁垂直强度极化法分频特征及预报指标建立”(2021010413)和“冷龙岭断裂东段构造地球化学特征研究”(2021010308);青海省地震局基金课题“高压直流输电线路对电磁观测影响的定量分析”(2021A03)和“地磁水平椭圆极化法在青海地区的应用”(2020A01)联合资助。

摘　　要：地磁加卸载响应比方法作为当前提取地震磁异常手段之中较流行的方法之一,具有物理机制明确、计算便捷、对应地震较好的特点.2020年12月26日地磁加卸载响应比计算结果显示甘青川9个台站高比值变化,时间上,表现为同步单日尖峰形态,异常占比7%;空间上,甘青川与川青藏交界显示两个高值区域,其中青海巴塘地磁加卸载变化幅值最大,为3.9.该高值变化出现147天后发生2021年玛多7.4级地震,震中位于川青藏交界异常区边界,距离阈值线70 km.玛多地震孕震过程中,因区域应力改变导致部分断层偶然发生错动,使得地壳中产生感应电流,从而生成变化磁场,利用地磁加卸载响应比方法提取的异常阈值线是感应电流集中分布区的表现形式之一.综合分析认为,2020年12月26日地磁加卸载响应比同步高值变化与玛多地震有一定关联.As far as we know,the geomagnetic load-unloading response ratio method is one of the most popular and effective methods to extract seismic magnetic anomalies.The calculation results of geomagnetic load-unload response ratio on December 26,2020 showed that the high value of nine stations in Gansu,Qinghai and Sichuan province.In terms of time,it showed synchronous one-day spike pattern,accounting for 7%of the abnormality.In space,there are two high value regions at the border between Gansu-Qinghai-Sichuan and Sichuan-Qinghai-Tibet.On May 22,2021,an M_(S)7.4 earthquake occurred in Maduo County,Qinghai Province after the high value changed,the epicenter is 70 km from the threshold line.During the seismogenic process of Maduo earthquake,due to the change of regional stress,some faults were accidentally misplaced,which generated induced current in the crust and generated variable magnetic field.The abnormal threshold line extracted by the method of geomagnetic load-unload response ratio was one of the forms of the concentrated distribution area of induced current.According to the comprehensive analysis,the variation of the high synchronous value of the geomagnetic load-unload response ratio on December 26,2020 is related to the Maduo earthquake to a certain extent.

关 键 词：地磁加卸载响应比 甘青川地区 青海玛多M_(S)7.4地震 区域地磁异常 

分 类 号：P315[天文地球—地震学]