积石山M_(S)6.2地震前地电场异常特征  

Anomaly Characteristics of Geoelectric Field before Jishishan M_(S)6.2 Earthquake

作　　者：张丽琼 高曙德 李娜 ZHANG Liqiong;GAO Shude;LI Na(Gansu Earthquake Agency,450 West-Donggang Road,Lanzhou 730000,China)

机构地区：[1]甘肃省地震局,兰州市730000

出　　处：《大地测量与地球动力学》2025年第4期367-372,共6页Journal of Geodesy and Geodynamics

基　　金：中国地震局地震科技星火计划(XH24047YA);地震科学联合基金(U2039206);中国地震局震情跟踪课题(CEA-ZQGZ-202501049);甘肃省地震局地震科技发展攻关项目(KY2203002)。

摘　　要：利用大地电场优势方位角方法对2023年积石山M_(S)6.2地震震中400 km范围内的地电场资料进行优势方位角异常变化和特征分析。结果显示,震前最早出现异常的是位于海原断裂和六盘山断裂交会处的固原台,异常持续期间位于海原断裂中段的景泰台也出现方位角快速、显著偏转,2个台站的方位角α变化均为偏离正常背景值最大约45°,为中短期异常;最后出现异常的是位于巴颜喀拉地块的大武台,其方位角α出现快速偏转和突跳,偏离正常背景值最大约90°,为短期异常。3个异常台站数量符合大地电场优势方位角预测指标体系,异常演化过程中呈现异常出现、持续和结束时间具有准同步性的特点。从震中距来看,固原台最远,景泰台和大武台更靠近地震震中,震前由于板块内部挤压,3个地电场台站所处区域及周边应力挤压变化剧烈,当岩石受压破裂时,岩体裂隙结构导致地电场优势方位角相继发生显著变化,而震后3个地电场异常相继结束也间接反映出应力释放后岩体裂隙结构逐渐恢复的过程,说明3个台站的资料变化可以真实反映地下介质的变化情况。By utilizing the method of dominant azimuth of the geoelectric field,an analysis of the dominant azimuth anomaly changes and characteristics was conducted on the geoelectric field data within a 400 km range of the epicenter of the 2023 Jishishan M_(S)6.2 earthquake.The results show that the earliest anomaly before the earthquake occurred at the Guyuan station,which is located at the intersection of the Haiyuan fault and the Liupanshan fault.During the period of the anomaly,the Jingtai station,located in the middle section of the Haiyuan fault,also showed a rapid and significant deflection of the azimuth.The max azimuthαchanges at both stations deviated from the normal background value by about 45°,which is considered a medium to short-term anomaly.The last anomaly to appear was at the Dawu station,located in the Bayan Har block,where the azimuth angleαshowed a rapid deflection and jump,deviating from the normal background value by about 90°,which is considered a short-term anomaly.The number of three abnormal stations meets the prediction index system of the geoelectric field dominant azimuth.The evolution of the anomaly shows that the anomalies have quasi-synchronous characteristics in terms of appearance,duration,and end time.In terms of the distance from the epicenter,Guyuan station is the farthest,while Jingtai and Dawu stations are closer to the earthquake epicenter.Before the earthquake,due to the internal compression of the plate,the areas where the three geoelectric field stations are located and the surrounding stress compression changes were intense.When rocks were subjected to pressure and fracture,the fracture structure of the rock mass led to significant changes in the dominant azimuth of the geoelectric field in succession.The subsequent end of the three geoelectric fields anomaly after the earthquake also indirectly reflected the process of the gradual recovery of the rock mass fracture structure after stress release,indicating that the data changes of the three stations can truly reflect the c

关 键 词：大地电场 积石山M_(S)6.2地震 优势方位角 异常特征 

分 类 号：P315[天文地球—地震学] P319[天文地球—固体地球物理学]