Elucidation of historical volcanic phenomena and their mechanisms based on historical records - towards the establishment of a new generation of analytical methods

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K04079
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17030:Human geosciences-related
• Research Institution: Chiba University
• Principal Investigator: TSUKUI Masashi 千葉大学, 大学院理学研究院, 教授 (50192191)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 史料 / 雲仙岳寛政四年噴火 / 島原大変 / 富士山宝永噴火 / 噴火推移 / 山体崩壊 / 降灰分布

Outline of Final Research Achievements

Historical materials (such as old documents and drawings) contain absolutely necessary information for elucidating the sequence of a single eruption episode and the mechanisms of various volcanic phenomena during historical periods.
In this study, I reconstructed the 1792 eruption (in the Kansei Era) of Unzendake in Nagasaki Prefecture and the sector collapse of the Mayuyama lava dome, which caused the largest number of fatalities in historical times in Japan, and considered the mechanism of the collapse. Furthermore, focusing on the 1707 eruption (in the Hoei Era) of Mt. Fuji, I carefully reviewed historical materials and reconstructed the volcanic phenomena, and illustrated the daily distribution of ash and sandfall. The actual sequence of Mt. Fuji's Hoei eruption was successfully reconstructed with high precision and high resolution.

Free Research Field

火山地質学

Academic Significance and Societal Importance of the Research Achievements

歴史時代の史料が火山現象の高精度，高分解能の推移や機構の解明に非常に役立つことを雲仙普賢岳寛政噴火・島原大変，富士山宝永噴火を事例として示した．
(1)島原大変の山体崩壊のメカニズムとして地下水位の上昇と液状化が重要で，浅間山天明噴火の鎌原土石なだれのメカニズムと統一的に理解できる共通性について考察し，発表した．
(2)宝永噴火の降砂域を日にち・時間ごとに示した．既往研究にある16日間の累積降砂深の図や，風向きを与えたうえでのシミュレーション結果図に対して，本課題の成果で，現実の噴火の実態がより明らかになった．防災対策を考えるうえで重要な基礎資料となる．