Abstract: The geoelectric data recorded at Tengchong station located in southwest Yunnan province since 1986 were analyzed. Aiming at the polarization feature of geoelectric field before 4 distant and moderate local earthquakes, the results show that the polarization of geoelectric field gradually became linear during 3 months before earthquakes, which is different from the normal times when the data were discrete. The stronger the earthquake was, the earlier the linear polarization feature occurred. The polarization direction of geoelectric field was related to the azimuth of the epicenters, while there is close connection with the striking of active faults in focal area. Synthetically analyzing the mechanism of this kind of anomalies, it is thought that the anomalous geoelectric field signals might come from the focus and the fractures in focal area might be the best channel for the fluid flowing and propagation. The preseismic linear polarization feature of geoelectric field is typically imminent, which is of some significance in location and time prediction of future earthquakes.

Key words: Geoelectric field, Tengchong station, Linear polarization, Imminent prediction