摘要
应用吉林省内榆树、四平两个地电阻率台站观测资料,采用形态法、归一化变化速率法和各向异性度法,分析研究了1999年汪清MS7.0深震以及2006年乾安—前郭MS5.0浅源地震前的地电阻率异常变化.结果表明,震前地电阻率出现长趋势下降变化或短临异常变化,表现为:①汪清MS7.0深震前,榆树台和四平台地电阻率月均值曲线上均显示出震前持续2年尺度的中期下降异常;②汪清MS7.0深震以及乾安—前郭MS5.0浅源中强震前,榆树台和四平台地电阻率变化速率均大于异常指标;③乾安—前郭MS5.0地震前,四平台地电阻率各向异性度曲线显示出明显的低值异常变化,而榆树台各向异性度S曲线则出现破年变变化.上述异常变化的原因可能为,太平洋板块向NW方向挤压,导致震源区及附近最大主压应力方位(或近于该方位)NW向的挤压作用突出,引起介质内部导电流体快速进入或重新分布,从而使地电阻率出现长趋势下降变化和各向异性变化.
This paper studies the anomalous changes of earth resistivity before 1999 Wangqing MS7.0 earthquake and 2006 Qian＇an-Qianguo MS5.0 earthquake observed at Yushu and Siping stations of Jilin Province.The results show that,at the Yushu and Siping stations a long-trend decreasing or short-impending anomaly of earth resistivity appeared before the two earthquakes.Monthly mean curves of earth resistivity displayed two-year decrease anomalies at Yushu and Siping stations before the Wangqing earthquake.Before Wangqing and Qian＇an-Qianguo earthquakes,normalized variation rates of earth resistivity are larger than anomaly index at Yushu and Siping stations.Before Qian＇an-Qianguo earthquake,earth resistivity anisotropy degree showed obviously low value anomaly at Siping station,and at Yushu station it broke its annual variation value.Possible reasons for the anomalous changes maybe are related to the maximum principal compressive stress orientation＇ s （or close to the range） compressing NWwards in the source region and its vicinity resulting from NWwards extrusion of Pacific Plate,which makes the conductive fluid in the media quickly enter or redistribute,so that the earth resistivity shows a long-trend decrease and anisotropic variation.
出处
《地震学报》
CSCD
北大核心
2014年第3期452-463,532,共12页
Acta Seismologica Sinica
基金
中国地震局"地震监测
预报
科研三结合"课题(201112
140701)资助
关键词
地电阻率
地震
震兆异常
异常形态
归一化变化速率
各向异性度
earth resistivity
earthquake
earthquake precursor anomaly
shape anomaly
normalized variation rate
anisotropy degree
