Aftershock Activity in the Vicinity of Kyoto

Abstract

During the period from 1964 to 1968 about 50 earthquakes with a magnitude of 3.0 or greater occurred in the vicinity of Kyoto. These earthquakes are studied on their aftershock activity. Earthquakes of more than about 4.0 magnitude are accompanied by aftershocks almost without exception. Most of the earthquakes studied here did not have enough aftershocks that the customary statistical analyses of aftershocks-their time and spatial distributions, energy release and magnitude-frequency relation for aftershocks-are feasible. In this paper the aftershock activity of each earhtquake is examined in relation to the regional variation in two ways; one is the magnitude relation between the main shock and its largest aftershock; the other is the number of aftershocks. No significant feature can be obtained from the former examination, but the latter leads to an interesting observation about the regional variation of aftershock activity: that the earthquakes occurring in the southern part of the region concerned are followed by more aftershocks than those in the northern part.