Abstract: In this paper, the differences of precursory anomalies between strong earthquakes with M≥ 7 and moderate earthquakes with M= 5~ 6 were com pared and analyzed. The results indicate that there are not anyessential differences, but obvious quantitative differences between them. Prediction efficacies for increase of seismicity with M5~ 6 before an earthquake with M≥ 7 and increase of seismicity with M4~ 5 before and earthquake with m= 5~ 6 were also statistically examined and were passed, respectively.

Key words: Strong earthquake with M𢙗, Moderate earthquake, Precursor anbsurface, essential difference