抄録
Spatial and temporal distributions of epicenters of great shallow earthquakes suggest three migration branches during the last thirty years. In the north-western circum-Pacific seismic belt, which is one of the three migration branches, the epicentral regions of recent great earthquakes were systematically displaced from Japan to Alaska. In this sequential occurrence of great earthquakes, the considered seismic belt was nearly continuously covered by aftershock areas of these earthquakes without any appreciable overlap of aftershock areas. This marked feature provides some important suggestions on the mechanism of earthquake generation.
