火山噴火と地震の時・空関係-日本付近の大地震について-

Abstract

Seismic and volcanic data during this century reveals that most of all eruptions in Japan should be followed by large earthquakes (M ≧7.0) in concerned places. The time-space relation between major eruptions and great earthquakes larger than M7.7 in Japan shows a reverse correlation given by the following equation.T=50.61-18.17logDT: Interval from the starting time of an eruption to the occurrence time of the earthquake. D: Distance from the concerned volcano to the epicenter of the shock. This implies that the eruption occurs in earlier time prior to the concerned shock if the epicenter of the earthquake is nearer from the volcano. Based on this relation, the crustal breaking time in the estimated epicenter should be known. This suggests that the eruption occurs by the increased stress generated from the epicentral region. The increased strain should squeeze up magmas before breaking the crust. Recent eruptive activities strongly suggest that the strain has been critically accumulated in several regions such as northern and southern parts of central Japan and eastern Kyushu.