- 著者
- SHIMOZURU Daisuke
- 出版者
- 日本自然災害学会
- 雑誌
- Natural disaster science (ISSN:03884090)
- 巻号頁・発行日
- vol.5, no.2, pp.15-31, 1983
- 被引用文献数
- 4
A hazard assessment of a possible future eruption of Mount Fuji was made from data in old documents recording the tephra fall of its 1707 eruption. The thickness of basaltic scoriae and ash in 120 localities as far away as Tokyo was found from historical records. An isopach map was drawn from thes data which is in good agreement with the isopach map made by Tsuya based on his volcano-stratigraphic study. The major axis of the isopachs coincides with the prevailing wind direction during the corresponding months as recorded at the Weather Observatory on the summit of Mount Fuji. Old documents prove that the delay in the tephra fall between Odawara and Tokyo is approximately one hour, enough time for diaster warnings to be given. An eruption of Mount Fuji in the near future is likely after its long period of dormancy and probably will be explosive as was the 1707 eruption. Thus, the volcanic events of the 1707 eruption are considered a good basis from which to make a hazard assessment of Mount Fuji. A hazard map was drawn from the data collected on this 18th century eruption.
- 著者
- CHIGIRA,Masahiro
- 出版者
- Japanese Group for the Study of Natural Disaster Science
- 雑誌
- Natural disaster science
- 巻号頁・発行日
- vol.4, no.2, 1982
A peculiar "collapsing" landslide occurred at Nanamawari, Mitaka-iriya, on the Izu Peninsula during the 1978 Izu-Oshima-Kinkai earthquake. Field invstigations showed the causes and phenomena connected with this slide. The landslide began on a slope of 25゜with the sliding of scoria, soil and part of paleosol. The sliding surface was formed within the upper part of the paleosol, probably in a weathered ash bed, several meters below the original surface of the slope. During of transportation, the sliding materials disintergrated into dry debris and flowed onto the flat surface across the river, dashed against the opposite slope then rebounded and settled in a lobe-shaped deposit with lateral ridges and a distal mound. The landslide continued less than 30 seconds, but its maximum velocity was more than 11.7 m/s. The basic causes of the landslide were insufficient lateral support by strata on the lower and weak halloysite-rich paleosol in which the sliding surface formed. The landslide at Nanamawari is considered a special type of slide found in Japan.