Abstract: Based on analysis of the temporal and spatial characteristics of strong earthquake activities in mainland China, this paper studies the M≥7 earthquakes in mainland China from 1901 by Fisher method. The states of strong earthquake activities can be divided into intermittent phase, sporadically occurring phase and frequently occurring phase. Then based on this division, we discussed the spatial characteristics of earthquakes before one frequently occurring phase and the main area of strong earthquakes of the frequently occurring phase. The result indicates that there is an obvious difference of temporal and spatial characters of strong earthquake activities between the period of time before 1955 and after 1955. Before 1955, the duration of intermittent phases is shorter and the duration of frequently occurring phases is longer, and the main activity areas are the borderlines of the big triangle including the west of mainland China and its circumjacent areas. On the other hand, after 1995, the duration of intermittent phases is longer and the duration of frequently occurring phases is shorter, and the main activity areas are Huabei, the South-north earthquake belt, the Bayankala block. The main areas of different frequently occurring phase are alternant. The strong earthquakes of intermittent phase and sporadically occurring phase sometimes occurred in the main area of last frequently occurring phase or correlative with the main area of next frequently occurring phase.

Key words: Mainland China, Strong earthquake activity, Temporal and spatial characteristics