2018年松原M5.7地震前地电阻率变化特征研究

Anomaly Analysis of Geoelectrical Resistivity Observations Before 2018 Songyuan M5.7 Earthquake

采用年变、归一化速率法和各向异性度提取和分析了松原M5.7地震前四平台、榆树台、绥化台地电阻率资料异常,结果表明:(1)震前地电阻率1~2年左右时间出现中期异常,归一化速率法还出现一定的短临异常,但未有临震异常出现;(2)归一化速率法和各向异性度都是在出现正异常之后发震;(3)三种分析方法的异常形态、幅度各不相同,反映出三台资料存在明显的各向异性。这与各台的地质构造、裂隙走向、主压应力方向、发震构造与破裂方向、台站与震中的相对位置等具有关联性。

The anomalous changes of geoelectrical resistivity before Songyuan M5.7 earthquake are observed at Siping,Yushu and Suihua Seismic Station by annual variation,normalized variation rates method and anisotropy degree. The resules show that:(1) 1-2 years medium-term anomalies of geoelectrical resistivity would appeare before earthquake occured. There were some short-term and imminent anomalies of normalized variation rates method. However,there was no imminent anomalies;(2) An earthquake followedbypositive anomaly of normalized variation rates method and anisotropy degree;(3) The abnormal forms and rangea of the three analysis methods are different,reflecting the obvious anisotropy of the three station. It was related to the geological structure of each station,fracture direction,main pressure stress direction, seismogenic structure and rupture direction, the relative position of the station with the epicenter,et al.