Abstract:The available studies have shown that the three factors:reservoir water level elevation, water level change rate and specific water level elevation can affect the reservoir seismic activity. In order to comprehensively discuss the three factors, we introduce the fuzzy mathematical methods, define the membership function of the reservoir water level and consider the fluid diffusion mechanism hypothesis of reservoir earthquake, and then discuss how to select a subordinate function threshold, and how long that the water will affect the seismic activity. On this basis, a quantitative study method for the relation between the water level changes and seismic activity is given. With the method we studied the relation between earthquakes and the water level of three reservoirs in Shanxi Zhejiang, Shuikou Fujian, Xinfengjiang Guangdong.The results show that the initial water level of
reservoir is the main external factor affecting seismic activity in the reservoir area, but the impact time of three reservoirs are different that in Xinfengjiang Reservoir is about six years, the Shuikou Reservoir about five years, Shanxi Reservoir about 4 years.