桜島火山における噴火予知の研究

Abstract

The National Project for the Volcanic Eruptions Prediction in Japan has started in 1974. The 1st five year project was achieved in 1974-1978, the 2nd in 1979-1983, the 3rd in 1984-1988 and the 4th in 1989-1993. The outline of individual program based on the National Project at Sakurajima volcano is described in this paper during last twenty years.Totally, a three-dimensional network in and around the volcano edifice by 4 sites on ground based, 4 bore holes with lOOm in depth and 3 bore holes with 300m in depth, a wide area network covering three calderas of Kakuto, Aira and Ata by 8 sites of shallow pit with 20m in depth, an array with short span by 3 bore holes with lOOm indepth, 3 stations for soil gas, 5 sea-tidal stations around the volcano island, 14 seismic stations covering Kirishima Volcanic Belt-zone using PC-communication system and a precise monitoring site for ground deformation of the summit area using water-tube tiltmeters and extensometers have been established. Our monitoring items by above mentioned networks are earthquake, tilt, extension and contraction, sea level, shock wave, telluric magnetism, ground temperature, water level in bore hole, volcanic gas and hydro-accoustics.Also, the outline of researches concerning the prediction of volcanic eruptions and reducing volcanic hazards are introduced. For example, the automated warning system for the summit explosive eruption, the lava flow simulation, the generating procedure of volcanic earthquakes along the conduit beneath the summit crater and a model of Sakurajima volcano composed by the results obtained such researches as above mentioned.