2023年12月18日甘肃积石山M_(S)6.2地震前地电阻率异常特征及机理分析  

Variations of apparent resistivity and its possible seismogenic mechanism before the 18 December 2023 Jishishan M_(S)6.2 earthquake in Gansu province, China

作　　者：李新艳 解滔[3] 刘小鹏[1,4] 曾宪伟 卫定军[2] 崔瑾[2] LI XinYan;XIE Tao;LIU XiaoPeng;ZENG XianWei;WEI DingJun;CUI Jin(School of Civil and Hydraulic Engineering,Ningxia University,Yinchuan 750021,China;Earthquake Agency of Ningxia Hui Autonomous Region,Yinchuan 750001,China;China Earthquake Networks Center,China Earthquake Administration,Beijing 100045,China;School of Geography and Planning,Ningxia University,Yinchuan 750021,China)

机构地区：[1]宁夏大学土木与水利工程学院,银川750021 [2]宁夏回族自治区地震局,银川750001 [3]中国地震台网中心,北京100045 [4]宁夏大学地理科学与规划学院,银川750021

出　　处：《地球物理学报》2024年第10期3721-3734,共14页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(42071230);地震预测开放基金(XH24007D);地震科技星火计划(XH21050Y,XH20064);宁夏自然科学基金项目(2022AAC03692)资助。

摘　　要：2023年12月18日甘肃积石山县发生了M_(S)6.2破坏性地震,造成了较大的人员伤亡.震前1年左右开始,震中400 km内5个具有稳态观测的地电阻率台站多个测道陆续出现了不同形态的异常变化,其中甘肃武胜驿台、定西台、通渭台(包括地表和井下)和武威台表现为以年变幅减小/快速下降变化为主的负异常,武都台则表现为年变幅增大的正异常.本文基于ERA5同化数据集中不同深度的土壤温度和土壤水分,定量化拟合了不同水热条件下各台站/测道正常年变形态,在此基础上排除了测区环境变化对异常形态影响.结合岩石物理实验结果和断层虚位错模式,讨论了地电阻率异常变化与孕震过程之间的联系.结果显示,存在负异常变化的武胜驿台、定西台、通渭台和武威台位于地震孕育过程产生的挤压增强区,而存在正异常变化的武都台处于相对膨胀区.求解了存在地电阻率异常变化区域GNSS面应变时间序列,结果发现,在地电阻率负异常变化台站附近的变形单元内以面压缩为主,而在正异常变化的武都台附近,变形单元内以面拉张为主.GNSS面应变揭示的介质变形特征与虚位错模式中的挤压增强区和相对膨胀区相吻合,表明了5个台站地电阻率变化与此次积石山M_(S)6.2地震孕育过程之间可能存在“介质变形-地电阻率变化”形式的关联.The destructive earthquake (M_(S)6.2) occurred in Jishishan County, Gansu Province, northwestern China on December 18, 2023, which resulted heavy casualties. The various anomalies of apparent resistivity were recorded a year before the earthquake occurrence at five observation stations in an area within 400 km around the epicenter, which include negative anomalies showing decreased annual changes or high decreasing rates at the Wushengyi, Dingxi, Tongwei (including surface observation and borehole observation) and Wuwei stations;as well as positive ones showing increased annual changes at the Wudu station. For quantitative analysis of the normal annual variations in apparent resistivity, soil temperature and soil water content at different depths from the ERA5 assimilation datasets (ECMWF Reanalysis v5) were used to eliminate environmental effects on the anomalies. The apparent resisitivity data combined with the rock physics experiment and the virtual fault dislocation model indicate possible relationship between the seismogenic mechanism and anomalies of apparent resistivity. The negative anomalies with decline changes of apparent resistivity at the Wushengyi Dingxi, Tongwei and Wuwei stations occurred in an enhancement area of compressive stress related to the seimogeinc process of the Jishishan earthquake. While the positive anomalies at the Wudu station occurred in the areas of relative extension. Moreover, the surface strain calculated by GNSS time series near the area of apparent resistivity anomalies demonstrates that the distribution of apparent resistivity anomalies with decline changes are spatially consistent with the compression zone, but the Wuwei station in the expansion zone of GNSS surface strain, which coincides with the result of the virtual fault dislocation model. Therefore, the relationship between the changes of apparent resistivity at the five stations and the seismogenic mechanism of the Jishishan M_(S)6.2 earthquake can be described in term of the deformation-apparent resistivity variati

关 键 词：地电阻率 年变化 土壤水分 虚位错模式 介质变形 

分 类 号：P315[天文地球—地震学]