Abstract: The relationship between the areas with geoelectric precursors and the areas with group earthquakes in North China and western China is investigated in this paper, and the dynamic process of anon-dimensional parameter of ground resistivity (Rd) observed during Tangshan M_S 7. 8 earthquake is analyzed. The result shows that the geoelectric signals could bring information regarding the time, location and magnitude of group strong earthquakes, which provides evidence for earthquake prediction. It is also described how to correlate the period of trend anomalies in ground resistivity with the magnitude of the future earthquakes; the abnormal areas with the seismo genic areas; and the short -term to imminent anomalies in geoelectricity with imminent earthquake prediction. That gives new ides and has got beneficial results in practice.

Key words: Non-dimension parameter of g round resistivity (Rd), Trend anomaly in geoelectricity, Short-term to imminent geo electric anomalies, Precursors in geoelectricity, Dynamic process