基于重磁场年变化联合分析马尔康M_(S)6.0地震特性  

Research on the characteristics of the Maerkang M_(S)6.0 earthquake based on the joint analysis of annual changes in gravity and magnetic fields

作　　者：刘东 赵育飞 张勇[1] 黄江培 吴宇琴 Liu Dong;Zhao Yufei;Zhang Yong;Huang Jiangpei;Wu Yuqin(Yunnan Earthquake Agency,Yunnan Kunming 650224,China;School of Surveying and Mapping,Wuhan University,Hubei Wuhan 430070,China)

机构地区：[1]云南省地震局,云南昆明650224 [2]武汉大学测绘学院,湖北武汉430070

出　　处：《地震科学进展》2024年第11期820-830,共11页Progress in Earthquake Sciences

基　　金：云南省地震局2024年度科技专项(2024X04);武汉引力与固体潮国家野外科学观测研究站开放基金(WHYWZ202103)项目联合资助。

摘　　要：利用川西地区2017—2021年多期地面重力观测和地磁观测资料,对马尔康MS6.0地震进行分析,并使用重磁场年变归一化融合分析结果对地震的发震位置进行分析,获得了融合分析结果和马尔康地震要素之间的相关关系。结果表明:区域重力场异常变化与川西地区断裂带在空间上关系密切,马尔康震中地区重力场变化较为微弱,变化量等值线始终在零值线左右,但在周边地区变化剧烈;岩石圈磁场年变化结果显示,震前岩石圈磁场水平矢量从区域整体弱变,到震中持续弱变和外围整体趋同后反向弱变,弱变量级较小且方向散乱;融合归一化震前一年期重磁场年变化数据,根据核密度曲线的重叠范围和峰值差较小的条件,可以判定出强震发震的区间范围(30°N~33°N,101°E~104°E),2022年6月芦山M_(S)6.1和马尔康M_(S)6.0地震就发生在该区间范围内。进一步将川西地区按1°×1°的格网划分后,马尔康地区重磁变化核密度曲线峰值差逐年减小,并在发震前重力变化和地磁变化峰值差达到最小。马尔康地区重力场和岩石圈磁场的磁化率变化在孕震过程中逐年趋于一致,证明了区域内存在物质和能量的交换和动力作用,引起了活动断层物质变迁和构造变形,在地表产生了相应的重力变化和岩石圈内磁场变化。重磁场的年变融合分析对强震发震位置的判定具有一定的指导意义。Using multi-period ground gravity and geomagnetic observation data from 2017 to 2021 in western Sichuan,the M_(S)6.0 earthquake in Maerkang was analyzed.The results from the annual variation normalization fusion analysis of gravity and magnetic fields were applied to study the seismic location of the earthquake.A correlation between these fusion analysis results and elements of the Maerkang earthquake was established.The findings indicate that regional gravity field anomalies are closely related to fault zones in western Sichuan.In the epicentral area of the Maerkang earthquake,gravity field changes were relatively weak,with the change contour consistently near the zero line,while surrounding areas experienced significant change.The annual variation of the lithospheric magnetic field revealed that the horizontal vector of the magnetic field weakened overall before the earthquake,with the epicentral region continuing to weaken and the periphery converging,followed by a reverse weakening.The weak variations were small in magnitude and directionally scattered.By integrating normalized annual variation data of gravity and magnetic fields from the year before the earthquake,the interval range for strong earthquake occurrence was determined based on the overlap of the kernel density curve and the condition of small peak differences(30°N~33°N,101°E~104°E).Notably,the M_(S)6.1 Lushan earthquake and the MS6.0 Maerkang earthquake both occurred within this interval range in June 2022.After dividing the western Sichuan region into 1°×1°grids,it was found that the peak difference in the gravity and magnetic variation kernel density curve in the Maerkang area decreased year by year,reaching its minimum before the earthquake.The changes in magnetic susceptibility of both the gravity and lithospheric magnetic fields in the Maerkang region showed year-to-year consistency during the seismogenic process.This consistency suggests the exchange and dynamic interaction of matter and energy within the region,leading to material c

关 键 词：重力异常 归一化 核密度曲线 岩石圈磁场总强度 

分 类 号：P315.63[天文地球—地震学]