Basic research on eruption history for preparing hazard maps of the active volcanoes in Central Kyushu, Japan

日本九州中部有四座活火山，即都见岳火山、九州火山、阿索火山和云仙火山。我们调查了火山的喷发历史。本研究的结果如下：1.作为云仙火山联合大学研究小组地质小组的成员，观察并描述了熔岩穹丘的生长顺序。日本地质调查局将在本财政年度末出版云仙火山的地质图。2.在距阿索破火山口约90 km处发现了被阿索-4火山碎屑流吹倒和烧毁的大树。这些树的出现为估算远区阿索-4火山碎屑流的温度和速度提供了重要信息，并阐明了阿索火山中岳15,000年来的喷发方式。根据这一结果，提出了中岳的初步危险图。鹤见岳火山爆发的现场证据在不到6,300年的时间里在火山脚下获得。一些调查结果在学术团体的一些会议上口头介绍。

Four active volcanoes, Turumi-dake volcano, kuju volcano, Aso volcano and Unzen volcano, are situated in the Central Kyushu, Japan. We have investigated eruption history of the volcanoes. The results of this study are as follows ;1. The sequence of the growing of lava dome was watched and described as a member of Geological Party, Joint University Research Group for Unzen Volcano.The Geological map of Unzen Volcano will be published by Geological Survey of Japan in the end of this fiscal year.2. Blown down and burnt big trees by the Aso-4 pyroclastic flow were found at about 90 km from the Aso caldera. The occurrence of these trees was very informative for the estimation of temperature and velocity of the Aso-4 pyroclastic flow at distant area.The mode of eruption of Naka-dake, Aso volcano, for the past 15,000 years are clarified. From this result, tentative hazard maps of Naka-dake were proposed.3. The field evidence of the phreatic explosions of Tsurumi-dake in the period younger than 6,300 years was obtained around the foot of the volcano.Some of the results of this investigation were orally presented on some meetings of academic society.