Based on uniform instrumental data, we have analyzed regularities in seismic activity on the Earth as a whole and in separate regions during 1897–1990 as well as the relationship between earthquakes of various intensity. The analysis confirms: (i) considerable variation in seismicity (against the background of a 10-fold increase in its intensity, semisecular quasi-periodicity is developed, which is complicated by S-year bursts of activity exceeding the levels of low-active periods more than by a factor of 10); (ii) time discrepancy in the processes of energy release during earthquakes of different intensity with a lag in the case of weaker earthquakes; (iii) synchronous seismic variations in seismically active regions with an area of about 4- 106 km2 in semisecular magnitudes of its parameters. The results obtained suggested that the development of seismicity of the Earth during the past centuries and millenia could be well reconstructed.
AV Chipizubov (Wed,) studied this question.