Abstract
The time variation of earthquake volume was investigated from the spatial distribution of aftershocks of both Tohnankai earthquake (1944) and Mikawa earthquake (1945). As these two great earthquakes occurred during the period of the World War II, there were not sufficient data which were published, but the available data concerning the aftershock activity were obtained by virtue of Nagoya Meteorological Observatory. Owing to these collected data the magnitude of all aftershocks were calculated by using the duration of preliminary tremors and the duration of oscillations. Thus the time variations of both released seismic wave-energy and energy-density were obtained.
It was found that the released wave-energy density varied from 1×104erg/cm3 at the time soon after the main shock to 4×103erg/cm3 at the time after one year passed in the case of Tohnankai earthquake and from 6×103 erg/cm3 to 1×103erg/cm3 in the case of Mikawa earthquake.
