Investigations of a phreatic explosion in Oct.1995 of the Kuju volcano and the following activities

1995年10月火山爆发后不久，在岩山地区周围设置了地震、地磁、大地测量学和温度变化等观测点，以掌握情况并阐明火山爆发的机制。关于库州火山周边地区的地震：1)大多数地震事件并非发生在新形成的火山口阵下方，而是集中在已存在多年的火山喷发区下方的浅层地下；2)陨石坑阵列南侧发生的事件较少；③火山灰喷发时期的事件源在火山口阵北侧呈垂直排列；④西部震源较岩山地区深，向岩山方向浅。除GPS外，所有大地测量点均位于新陨石坑阵列的北侧，其面积随时间以3-4.5 cm/月的速度收缩。1995年12月20日前后，地磁总强度由强向去强转变。根据对火山灰的分析，推测岩浆的顶部存在于距离地面2 ~ 5km的地方。从火山气体分析来看，高温气体成分似乎有所增加。

Soon after the phreatic explosion in October 1995 many observational points were installed for earthquakes, geomagnetism, geodetic-and temperature variations, etc.around the Iwoyama area to seize the situation and to elucidate the mechanism of the eruption. On earthquakes around the Kuju volcano area : 1) most events did not occur beneath the newlycreated crater array but were concentrated in shallow subsurface beneath the fumarolic area that had existed for ling ; 2) few events occurred on the southern side of the crater array ; 3) the sources of events during the periods of ash eruptions exhibited vertical alignment on the northern side of the crater array ; and 4) sources in the western area were deeper than those in the Iwoyama area and tended to be shallower toward Iwoyama. All the geodetic measuring points except those for GPS were located on the northern side of the new crater array and exhibited contraction of the area with time at a rate 3-4.5 cm/month. The totalintensity of geomagnetism converted its sense from magnetization to de-magnetization around Dec.20,1995. The top of the magma was presumed to exist at 2-5km blow the ground surface from analyzes of volcanic ashes. From volcanic gas analyzes high-temperature gas components seemed to increase.