A quantitative consideration of several calderas for study of their formation

Abstract

Gravimetric data have been accumulated on 22 calderas mainly in Japan. For sorne, explosion-seismic data or drilling results are also available. Synthesizing these data, sorne common features of their subsurface structure are deduced. Although all Japanese calderas are relatively young, ranging in age from 6 000 to 100 000 Y.B.P., a general discussion on them as a whole is tried: the mass deficiencies obtained by gravity anomalies over the calderas have a close correlation with their diameters. This correlation is similar to that of the meteorite cratcrs in Canada, implying the similarity in the subsurface structure between the calderas and the meteorite craters.