著者

Murai Isamu

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.40, no.4, pp.805-814, 1963-03-10

被引用文献数

2

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The eruption occurred suddenly at about 9:55 p.m. on June 17, 1962 at the Yake-dake Volcano. The outbursts did not occurr at the summit crater, but took place at the Kurodani Crater and the Nakaotoge Explosion Crater. New fissures were opened on the wall of the explosion crater. The entirety of ejected debris does not belong to the juvenile materials. They were brought from the pre-existing rocks on the upper part of the volcano. Discharge of ash and debris ceased on the evening of June 18. The total volume of ejected materials is calcu- lated as 2×105m3, and the total mass of them is 3×105 ton for the density of ash-fall deposits in a compact packing state is about 1.6. From the morning of June 18, minor mudflows occurred on the western steep slope of the summit. On the afternoon of June 19, other mudflows occurred from the edge of the fissure at the Nakao-toge, being accom- panied with intense noises and air shocks. These mudflows might have been caused by the flowage of over-saturated ash and debris piled on the steep slopes around the summit, where tremendous amount of water vapour contained in the eruption clouds condensed on the ground and wetted newly piled ash and debris. After the eruptions on June 17 and 18, some minor outbursts took place sporadically, i. e. on July 26 and on August 9, 1962.昭和37年(1962年)6月17日午後9時55分ごろ焼岳火山は突然爆発した.中尾峠の焼岳小屋は噴石で破壊され,管理人2名が負傷した.噴火は山頂北面の中尾爆裂口と西北中腹の黒谷火口で起こつた.中尾峠爆裂火口壁上には延長2kmにわたる割れ目があらたに開口した.火山灰や岩屑の抛出は翌18日午後にやんだが,多量の水蒸気を含んだ噴煙がひきつづいて噴出した.提出された岩屑の中で新たに岩漿から由来したと見られるものは見出されなかつた.18日午前中より19日までの間に,山頂北面の斜面に小規模な泥流が発生した.19日午後に烈しい音響がこの地方一帯に聞えたが,爆発や火山灰の噴出は認められなかつた.この音響の発生とほとんど同時に,中尾峠の割れ目の末端より泥流が流れだし,梓川の川岸まで達した.これらの泥流は,火口より噴出された多量の水蒸気が山頂付近の急斜面に堆積した火山灰上に凝縮したために発生したものと考えられる.21日