Seismic Space-time Evolution Characteristics in Tangshan old Seismic Region During the Past 40 Years

On basis of small earthquake catalog in Tanshan old seismic region during the past 40 years, using classic aftershock sequence analysis method, we analyze the time evolution characteristics of the Tanshan great earthquake aftershock sequence, and then, based on the principles of intensity scale, we analyze the time evolution characteristics of earthquake space image with different intensity of earthquake. On basis of accurate relocated small earthquake catalog, we study the small earthquakes intensive image characteristics since 1996. Referring to the research results of the Tangshan earthquake during the past 40 years, we thoroughly analyze the relationship between the aftershocks space-time evolution characteristics and tectonic. The results indicate that the activity of 1976 Tangshan M7.8 great earthquake aftershock sequence become weaker as time goes by, its intensity gradually diminished and its frequency is gradually lower, but the intensity fluctuation is obvious. There is still M5.0 earthquake occurred 36 years after the main shock, spatial distribution of seismic images have significant different characteristic before and after 1996.