Studies on history of volcanic eruption in Japan by correlation between old documents and eruptive deposits.

在Chokai东侧的Towada-a火山灰（公元915年）下方发现了一层灰色火山粘土。它与公元871年在日本三台实录中记录的喷发有关。据《日本三台实六》记载，两条巨蛇被认为是火山喷发时从两侧流下的两股活跃的熔岩流。在赤城南麓的9世纪的地平线上，镶嵌着地裂缝或碎屑雪崩和火山泥流沉积物等引人注目的地质特征<th>。它们与公元818年《瑞州国志》中描述的地震有关，但发震断层尚未发现。重现间隔估计为数万年一次。会荣公元1707年是富士山历史上唯一一次在东海-关东南部地区存在大量目击记录的火山爆发。这些记录被严格阅读，以澄清在16天的喷发期间发生了什么。在伊藤岛之神的日记中有详细的记载，并附有地图。在韩国济州岛（Mt. 1002年和1007年。这些火山爆发的基本文件是《高丽史》，它在世纪中期编辑时增加了信息。作为这些史料的背景，研究了东亚的自然哲学和意识形态，并指出它们与爆发时高丽政府的历史评价的关系。从十五世纪后半叶到二十世纪上半叶对这些火山爆发的报告的审查中，人们注意到，指定济州岛内火山爆发的具体位置的基础是薄弱的。

A layer of gray volcanic clay was found immediately below the Towada-a ash (AD 915) on the eastern flank of Chokai. It is correlated with the AD 871 eruption recorded in Nippon Sandai Jitsuroku. Two big snakes described in Nippon Sandai Jitsuroku were believed to be two active lava flows descending the flanks during the eruption.Conspicuous geologic features such as ground cracks or deposits from debris avalanches and lahars are embedded in the 9^<th> century horizon on the southern foot of Akagi. They are correlated with the AD 818 earthquake described in Ruiju Kokushi, however, the causative fault is yet to be discovered. The recurrence interval is estimated once in tens of thousand years.Hoei AD 1707 is the only eruption among historical eruptions of Fuji in which abundant eyewitness records exist in the Tokai - Southern Kanto area. Those records were critically read to clarify what happened during the eruption over 16 days. It is rediscovered that the eruption is described in detail by Ito-Shima-no-kami's Diary including pictorial maps.Two eruptions took place on the Korean island of Jeju (Mt. Halla) in 1002 and 1007. Fundamental document of these eruptions is History of Koryo, which has had information added when it was edited in the mid-fifteenth century. As background to these historical materials, the natural philosophy and ideology of East Asia are researched, and their relation with historical evaluations of the government of Koryo at the time of eruption is pointed out. From an examination of reports on these eruptions made from the latter half of the fifteenth to the first part of the twentieth centuries, it is noted that the basis for specifying the particular location of eruption within Jeju is weak.