文章摘要

文章信息/Info

Title:: The Variation of Geo-electric Field at the Dulan Seismic Station before the 2021 Maduo,Qinghai M_S7.4 Earthquake

Author(s):: LI Xia; ZHAO Yuhong; FENG Lili; LIU Lei; GOU Zhidong; SU Weigang; (Qinghai Earthquake Agency,Xining 810001,Qinghai,China)

Keywords:: the Dulan geo-electric field; the Maduo M_S7.4 earthquake; premonitorily abnormal characteristics; case-study of earthquakes

摘要:: 2021年青海玛多M_S7.4地震前,都兰地电场观测资料出现了显著异常变化。通过分析都兰地电场年变形态,长、短极距比值及经相关距平去除年变后时序图,并与2019年夏河M_S5.7地震的震前异常特征进行对比研究,得出以下主要结论:① 2020年7月原始地电场观测曲线均开始出现不同程度的破年变变化,且长、短极距6个测道同步变化,主要表现为年变减小,达到最低点后转折加速上升,其中以北南测道变化最为显著; ②地电场长、短极距测值比结果显示,各方向均在震前出现“V”字型变化,且幅度大、速率快; ③都兰地电场观测日均值经相关矩平法去除年变后,自2020年5月后曲线呈现出趋势性或快速下降的形态,区间变化值均小于2015—2020年均值水平,甚至低于两倍均方差水平,异常形态显著。综合分析认为,自2020年以来都兰地电场出现的异常变化与2021年玛多7.4级地震的孕育与活动过程具有一定关联。

Abstract:: On May 22,2021,an M_S7.4 earthquake occurred in Maduo County,Qinghai Province.Before the earthquake,the observed data of geo-electric field by the Dulan stotion shawed significant abnormal changes and were of credibility to some extent.And the form of the curve of the data is similar to that of the data before the 2019 Xiahe M_S5.7 earthquake.The main manifestations of the anomaly are as follows:Firstly,the original observed data showed anomalous annual variations in different degrees in July 2020,and the 6 survey channels of long distance and short polar distance changed synchronously.The annual variations mainly decreased and rose rapidly after reaching the lowest point.Secondly,the ratio of the observed data between the long polar distance and short polar distance of the geo-electric field showed that the V-shaped variations appeared sharply and rapidly in all directions prior to the earthquake.Thirdly,after the annual variation is removed by the Correlation Moment Plane method,the curves of the daily observed mean value of the geo-electric field showed a trend or a rapid decline after May 2020,and the interval change values are all less than the historic average level,or even lower than twice the mean square deviation level,and the abnormal form is significant.We believe that the abnormal variations of the geo-electric field in Dulan region since the year 2020 are related with the genesis and evolution of the Maduo M_S7.4 earthquake.