SOME STATISTICAL CHARACTERISTICS OF GLOBAL ACTIVITY OF LARGE EARTHQUAKES

Based on the uniform catalogue of large earthquakes of the earth studied and published by K. Abe, some knowledge about global activity of strong shocks might be obtained. (1) The global seismicity is in a stage of relative quiesence since the late 1960 's. (2) The b-value is lower in continental seismic regions than in other regions (belts); the b-value is lower during the seismically active period than in a quiet one. (3) According to cluster analysis, it may be recongnized that the seismically active and quiet episodes occur alternatively in different seismic regions. (4) There may be some correlation between the distribution of epicenters of large shallow earthquakes in continents of the northern semisphere and the change in velocity of the earth's rotation.The above characteristics might be referential for evaluating the tendency of earthquake occurrence in some seismic regions.