SOME NATURES OF THE EXPLOSIONS OF SAKURAJIMA VOLCANO FOLLOWING THE ASCENT OF LAVA

Abstract

A remarkable earthquake swarm was recorded by the seismometer at SakurajimaVolcanological Observatory from may 25 to 26, 1967, and on th 28 th of this month thefact that 40-50 tons of lava pool had formed at the bottom of Minamidake crater wasconfirmed by the airplane observation. From may 29 to June 28, a series of volcanicexplosions by which all this lava was ejected, took place.Same phnomenon was occurred once more from July 22 to Augst 10, 1967.Some natures of these series of volcanic explosions are summerized as follows:1. On three or four days after the lave pool is formed, the series of volcanic explo-sions hegines, and it last till the lava pool is disappeared.2. Ratio of the energy of air-vibration to that of earthquake, which were dischargedby a volcanic explosion, is small at the beginning of series, but as the series goes on itbecomes larger and larger.3. As for the time interval of the succesive explosions, more 60% of all is shorterthan 24 hours.