The subway operation causes significant interference to the ground electric field observation of Yingcheng Seismic Station,and the maximum interference amplitude was about 33 mV/km and the average interference amplitude was about 14 mV/km. In order to improve the quality of observation data,the time-frequency characteristics of the normal daily variation of the ground electric field and the interference data of Yingcheng Seismic Station are compared and analyzed. The filtering methods of mean filtering,empirical mode decomposition and mathematical morphology filtering are respectively used to filter the interference data. The filtering effects of several methods and the influence of the scale factor of morphological structure elements on the filtering structure are compared and analyzed. The results show that the means filtering and generalized morphological filtering can effectively remove the geoelectric field subway interference. The above two methods are recommended for the geoelectric field stations affected by subway interference to process the observation data,so as to improve their use efficiency.
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