Abstract: All geoelectric and geomagnetic data observed for 6 years at Tianzhu Sino-France cooperative station have been put on display (sampling period one day). We can see from them that before some moderately strong earthquakes occurred in western region of China, Tianzhu geoelectric field appeared a slow abnormal variation, and also a self-potential anomaly. There are 2 kinds of forms: a) at first showing increase, then decrease tendency variation, b) acceleration variation with large amplitude and single direction. In addition, before earthquake there is still short-term step anomaly in telluric field. A possible mechanism of several kinds of anomalies is roughly discussed in this paper. It is considered that among them the large amplitude acceleration variation belongs to magnetic storm, the obvious change of streaming potential before earthquakes results in tendency background variation, which only emerges before Kunlun Mountain earthquake with M_S=8.1 in 2001.

Key words: Geoelectric field, Self-potential, Anomaly, Earthquake