桜島火山の火山性微小地震と爆発の研究(1) ―火山性微小地震の発生様式による爆発の分類及び溶岩上昇時の爆発について―

Abstract

Volcanic explosions at the Minamidake crater of Sakurajima Volcano are classified intosix types, according to the mode of the occurrence of the volcanic micro-earthquakes beforeand after the explosion. The main results are as follows;1) The same type explosions are often repeated. This may be explained that the each typeexplosion represents the condition of the volcanic vent and the energy supply from the reservosr.2) The type of the large explosions are almost The D IV or the D IV' type.3) After the formation of the lava-lake in the crater, the D I type explosions occurre frequent-ly. From the arrival time difference of the sismic wave and the sonic one, the origin of the D Itype explosion is seemed to be shallower than that of the other type explosions. This fact isascertained by the another observation also, that is the observation of the angle of the incidence ofthe explosion earthquakes. Moreover the process of the occurrence of the D I type explosion isconsidered.