吉林地区地电阻率震兆异常对比分析

摘要

Pre-earthquake geoelectrical resisitivity anomalies of deep source and shallow source earthquakes in Jilin Province have been abstracted by morphological method,normalized rate change method and degree of anisot-ropy method.The results show that①pre-earthquake geoelectrical resisitivity displayed 1 ~2 years mid-term anom-aly,even short-term anomaly with mainly negative anomaly;②the original monthly mean of anomaly variation am-plitude of pre-earthquake geoelectrical resisitivity less than one percent,showing the increases of captures signal sensitivity by digital geoelectrical instrument,which inextricably links with the sandstone bedrock structure beneath stations;③anomalous variation existing in pre-earthquake geoelectrical resisitivity and recovery to normal morpholo-gy after earthquakes,reflecting the change of stress in underground epicentral area before earthquakes,and the re-turn and restoration process of regional tectonic stress field after earthquakes.%对采用形态法、归一化变化速率法和各向异性度法提取到的吉林省内深源地震以及浅源地震前的地电阻率异常变化进行对比分析，结果表明：①震前地电阻率出现1～2年尺度中期异常，甚至短期异常，异常以负异常为主；②震前地电阻率原始月均值异常变化幅度＜1％，表明数字地电仪捕捉电信号灵敏度的提高，更与台址构造密不可分；③震前地电阻率出现异常变化，震后恢复到正常变化形态，反映出震前震中区地下应力的变化，震后区域构造应力场重新调整并逐渐恢复的过程。