Abstract: A method used for finding the criterion for estimating earthquake tendency based on the hypothesis test of significance is proposed in this paper. Taking the annual number data of earthquakes since 1930 as an example, the criterion for estimating the possibility of occurrence for earthquakes with magnitude equal to or greater than 7 in mainland China by using annual number of earthquakes with magnitude equal to or greater than 5 is obtained. The results show that when annual number of earthquakes with magnitude equal to or greater than five N_a5 is equal to or greater than 31, we could make judgment that there would be no earthquake with magnitude equal to or greater than 7 occurring in the following sixth year, when N_a5 is less than or equal to 10, we could make judgment that there would be some earthquakes with magnitude equal to or greater than 7 occurring in the following sixth year, when N_a5 is in the range from 11 to 30, we can not make any judgment about whether there would be any earthquake with magnitude equal to or greater than 7 occurring in the following sixth year or not, and when N_a5 is equal to or greater than 24, we could also make judgment that there would be no earthquake with magnitude equal to or greater than 7 occurring in the following sixth year, but the possibility of making a mistake is 5%. Since N_a5 in 2002 is 7, it can be predicted that there would be some earthquakes with magnitude equal to or greater than 7 occurring in mainland China in 2008. N_a5 in 2003 is 28, it can be predicted that there would be no earthquake with magnitude equal to or greater than 7 occurring in mainland China in 2009 with the possibility of 5% for making a mistake. This method is also used for finding the criterion of other seismic or aseismic observation items for estimating seismicity tendency.

Key words: Hypothesis test of significance, Earthquake tendency, Criterion of judgment