Based on the strong earthquake catalogue, this paper discusses the characteristics of the time series of strong earthquake activities in the world, western Chinese mainland and its peripheral ＂big triangle seismic region＂, as well as the Chinese mainland. According to the analysis of the periodic features of global seismicity of M I〉 8. 0 strong events, it is found that there is significant difference in global seismicity before and after the 1960s. Statistical analysis with the Fisher method has revealed that the ＂big triangular seismic region＂ has experienced a process of M8.0 earthquake activity with a duration of over a hundred years since 1800. Further analysis shows that the global seismicity and the ＂big triangular seismic region＂ possibly has a period of a hundred-year scale, and has quasi- synchronicity to a certain extent. The shallow earthquake activity of Ms I〉 7. 0 in the Chinese mainland is obviously controlled by the seismicity in the big triangular seismic region and by global seismicity in a larger spatial-scale. In terms of the time series of these earthquakes, the seismicity shows a decadal and century-scale activity patterns.
