2021年5月22日玛多M_(S) 7.4地震周边地区岩石圈磁场变化及地震前后异常特征分析  

Variation of the lithospheric magnetic field in the surrounding area of the Maduo M_(S) 7.4 earthquake and the anomalous characteristics before and after the earthquake

作　　者：张瑜 陈双贵 马辉源 闫万生 杨磊 雷光 杨龙 杜建清 ZHANG Yu;CHEN Shuanggui;MA Huiyuan;YAN Wansheng;YANG Lei;LEI Guang;YANG Long;DU Jianqing(Gansu Earthquake Agency,Lanzhou 730000,China;Lanzhou National Geophysical Observatory and Research Station,Gansu Province 730046,China)

机构地区：[1]甘肃省地震局,兰州730000 [2]兰州地球物理国家野外科学观测研究站,甘肃730046

出　　处：《地震地磁观测与研究》2023年第3期64-72,共9页Seismological and Geomagnetic Observation and Research

基　　金：甘肃省地震局地震科技发展基金(项目编号:KY2303023);流动地球物理场观测项目(项目编号:ZX1803001);国家自然科学基金项目(项目编号:U2039206)。

摘　　要：利用2018—2021年连续4年流动地磁数据,分析了2021年5月22日玛多M_(S) 7.4地震前后周边区域岩石圈磁场部分要素变化特征,结果显示,震前1—3年岩石圈磁场水平矢量在震中100 km范围内出现了幅值减小、方向转向或无规律变化的弱变化现象,震中位于磁倾角、总强度、垂直分量的梯度带;震前1—2年,水平矢量的弱变化的特征更明显,弱变化区域更靠近震中,震中在磁倾角、总强度、垂直分量的“0”变线周围20km范围内;在震前2—3年,震中周边200km范围内,岩石圈磁场水平矢量方向与断层走向有较高的一致性;震后,水平矢量的弱变化现象消失。震前两期至震后一期结果显示,震中位置与磁偏角、磁倾角、总强度、垂直分量“0”变线的距离经历了“远—近—远”的过程,说明玛多震中地下应力的变化与上述要素“0”变线的分布关系密切,这些要素可以作为震磁异常的佐证。This paper analyzes the characteristics of variation in some elements of the lithospheric magnetic field in the surrounding area before and after the Maduo M_(S) 4.4 earthquake using four consecutive years of mobile geomagnetic data from 2018 to 2021,and concludes that the horizontal vector of the lithospheric magnetic field has a weak change suchas amplitude reduction,direction turning or irregular change within 100 km of the epicenter 1 to 3 years before the earthquake,and the epicenter is located in the gradient zone of the magnetic inclination,the total intensity,and the vertical intensity component;1 to 2 years before the earthquake,the weak change of the horizontal vector is more obvious,and the weak change area is closer to the epicenter,which is within 20 km around the zero variation line of the magnetic inclination,the total intensity,and the vertical intensity component.2 to 3 years before the earthquake,within 200 km around the epicenter,the direction of the horizontal vector of the lithospheric magnetic field is highly consistent with the strike of the fault.After the earthquake,the weak change inthe horizontal vector disappeared.The results from the two periods before the earthquake to the period after the earthquake show that the distance between the epicenter and the zero variation line of the magnetic declination,the magnetic inclination,the total intensity,and the vertical intensity component has gone through a“far near far”process,indicating that the changes of the underground stress at the Maduo earthquake epicenter areclosely related to the distribution of the zero variation line of the above elements,which can be used as evidence of the seismo-magnetic anomalies.

关 键 词：玛多M_(S) 7.4地震 流动地磁 “0”变线 矢量弱变化 

分 类 号：P315.721[天文地球—地震学]