十勝岳における1988〜1989年の爆発的噴火活動の地球物理学的研究 : 特集: 十勝岳1988〜1989年噴火

概要

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A series of 23 explosive eruptions had occurred at Mt. Tokachi (Tokachi-dake), central Hokkaido, Japan during December 16, 1988-March 5, 1989. This eruptive activity was preceded by 6 years of long-term but sporadic precursors and three months of irreversible culminating precursors. All eruptions were small scale, but characterized by explosive nature and often accompanied by small pyroclastic surges and/or pyroclastic flows. Geophysical aspects on those pre-eruption stages and explosive characteristics were discussed. One third of the 23 explosive eruptions were preceded by common immediate precursors; an increase of small low-frequency events. However, important eruptions, which produced pyroclastic flow or magmatic blocks, were not always preceded by such precursors. Knowledges of those abilty and inability was informed quickly to the officials and that resulted in an urgent introduction of a mud flow detection system, as a precautional measure to mitigate the possible occurrence of the 1926 type mud flow disaster, Only one eruption, the January 20 eruption, ejected essential materials including large blocks, Various observational evidences including extensive low-frequency tremor indicate the activated situation before this magmatic eruption. One possible explanation of this low-frequency tremor is the enforced magma injection to the vent system.
特定非営利活動法人日本火山学会の論文
1990-07-02