Abstract: The geoelectric field is an important part of the earth electro-magnetic field. Using the traditional time series statistical analysis method, this paper studies and discusses the variation characteristics of the second sampling data of the geoelectric field observed from Xiannushan seismic station, which belongs to the Chongqing municipality. The results show that: ① before and after Changning M_S6.0 earthquake, the anomalous change of the geoelectric field were recorded at Xiannushan seismic station, 390 km away from the epicenter; ② the average azimuth angle of the anomalous change was N77.55°E, approximately from the epicenter of Changning M_S6.0 earthquake to Xiannushan seismic station; ③ the typical anomalous change of the geoelectric field was intermittent and non-periodic disturbance, which densely appeared 8 days before the main shock of Changning M_S6.0 earthquake, lasted to the 4th day after the main shock, and then gradually transformed into the high-frequency disturbance changes; ④ the anomalous change of the geoelectric field appeared in lots of clusters, each of which is composed of multiple groups of step mutation with nonlinear attenuation. According to the comprehensive analysis, the anomalous change of the geoelectric field before and after Changning M_S6.0 earthquake, may be related to the filtered electromotive force generated by the high-pressure migration of the underground fluid, during the change of the structural fracture and the process of the rock micro fracture.

Key words: Changning M_S6.0 earthquake, Geoelectric field observation, Anomalous change, Second sampling data