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Title:: Temporal and Spatial Evolution of the Apparent Resistivity before and after the 2008 Wenchuan M_S8.0 Earthquake

作者:: 王同利¹; 崔博闻¹; 王丽红¹; 颜晓晔²; 李菊珍¹; (1.北京市地震局,北京 100080; 2.四川省地震局,四川成都 610000)

Author(s):: WANG Tongli¹; CUI Bowen¹; WANG Lihong¹; YAN Xiaoye²; LI Juzhen¹; (1.Beijing Earthquake Agency,Beijing 100080,China)(2.Sichuan Earthquake Agency,Chengdu 610000,Sichuan,China)

Keywords:: the Wenchuan M_S8.0 earthquake; apparent resistivity; time sequential analysis; spatial distribution; the Normalized Variation Rate method

摘要:: 采用归一化速率变化方法对2008年汶川M_S8.0地震震中周边19个定点台站观测到的地电阻率的时空变化过程进行了计算分析。时序分析结果显示:在汶川地震前,震中周边多个地电阻率台站准同步地出现了中短期前兆异常; 空间分布过程显示,地震孕震过程中地电阻率在震中区域有负异常丛集和由远及近的迁移现象,负异常丛集呈象限分布,长轴方向与震源机制解主压力方向基本吻合,且受孕震断裂、台站位置、观测装置布设方向等的影响。

Abstract:: In this paper,the Normalized Variation Rate method is used to analyze the sequential and spatial variation of the apparent resistivity observed by 19 stations around the Wenchuan M_S8.0 earthquake.The sequential analysis shows that some of the earthquake stations had quasi-synchronously recorded the short- and medium-term precursory anomalies of the apparent resistivity before the Wenchuan earthquake.The spatial analysis shows that in the epicentral region,the negative anomalies of the apparent resistivity had been featured with a strip distribution and with a migration from far to near before the earthquake.The cluster of the anomalies displayed a quadrant pattern,whose long axis was consistent with the direction of principal compressive stress of the focal mechanism solution.The seismogenic fault,the station location,and the layout direction of the observational instruments also influenced the distribution direction of the long axis of the precursory anomalies.