Abstract: The theory explanation has been done on the changes of the occurrence rate and accumulative time of the regional small earthquakes, from which it suggests that the occurrence rate and accumulative time of small earthquakes shows the direct proportion to the accumulative rate of the regional strain energy. When the occurrence rate takes different values and the accumulative time curve slope changes, the accumulative state of the regional strain energy is different. The accumulative time and occurrence rate of small earthquakes in different small regions along the Qilianshan-Liupanshan Earthquake Belt has been calculated. It has been showed that before the occurrence of moderately strong earthquakes both the curve slopes of the accumulative time and the occurrence rate of small earthquakes all change. It shows that before moderately strong earthquakes occur, the regional strain state change.

Key words: Small earthquake occurrence time, Accumulative time of small earthquakes, Regional strain energy, Qilianshan-Liupanshan Earthquake Belt