张掖MS 5.0地震前山丹地震台地电阻率异常分析

通过分析山丹地震台地电阻率资料发现，在2019年9月16日张掖M_S 5.0地震前地电阻率出现了明显的异常变化，即2016年11月开始EW测道观测数据出现年变畸变异常，年变幅度几近消失，该异常持续至2018年年底。采用傅里叶滑动去年变分析发现，同段年变消失，去年变后数值出现超阈值异常；采用矩平处理方法分析发现，2016年11月至2018年10月观测值小于矩平拟合值，出现低值异常。研究表明，该异常可能与2019年9月16日张掖M_S 5.0地震有关。

The precursor anomaly of earth resistivity at Shandan Seismic Station before Zhangye MS 5.0 earthquake

Through the analysis of the earth resistivity data at Shandan Seismic Station, it is found that before Zhangye M_S 5.0 earthquake on September 16, 2019, the earth resistivity observation shows obvious abnormal changes, that is, from November 2016, the annual variation of EW trace observation data appears distortion anomaly, the annual variation amplitude almost disappears, and the anomaly continues until the end of 2018. Using Fourier sliding removing annual variation analysis, it was found that the same period of annual variation disappeared, and the abnormal value after removing annual variation exceeded the threshold. Using the method of anomaly analysis, it was found that the observed value from November 2016 to October 2018 was smaller than the linearly fitting values, and a low-value anomaly appeared. The study shows that the anomaly may be related to the Zhangye M_S 5.0 earthquake on September 16, 2019.