Abstract: 24 earthquake with M≥6.0 occurred in China 's mainland from 1990 to 1996 are analyzed. The research results show that before about 80% of the strong earthquakes, the activity of earthquakes became active within and near the epicentral area. The anomaly is expressed in similar process,i.e., from a long-term quiescence, to moderate earthquake enhancement then a second quiescence just before strong shock, and finally the main shock occurs. The period from the quiescence just before strong shock till the earthquake occurrence is usually about several months to 2 years, with 10 months on average, which can be used as an index to judge whether the seismogenic process has been into the middleterm to imminent term for earthquake prediction. According to the acoustic emission experiments, the enhancement of the moderate seismicity could be taken as generalized foreshocks occurred at the end of the stable creep stage.

Key words: Moderate earthquake, Seismicity enhancement, Creep, generalized foreshocks