Abstract: Using the critical point concept, and ex tending Bow man 's idea on critical earthquake, we develop an intersecting circle method to locate critical region. A simulation check shows that this method is effective in finding a given critical regio n. We selected several real cases from New Zealand and China, and used this method to find the critical regions before the occurrence of large earthquakes. The result shows that this method is valid to detect a critical region and the epicenter of main shock might be in the critical region. We tried this method to find the critical regions of China with the data between January 1st, 1995 and August 31_st, 1999. The result show s that nearly all of those earthquakes with M (5. 0 occurred in China (except the Tibetan region) between August 31_st, 1999 and June 16_th, 2000 are situated in the critical regions.

Key words: Intersecting circle, Critical region, AM R Model