Data base of the volcanic ash fall distribution map of Japan.

Abstract

The whole total distribution map of the volcanic ash fall deposit in Japan was summarized with the data base under the program of the "Research on volcanic ash fall hazard assessment and risk management for industrial location" and the "Impact analysis on the volcanic ash-fall in the metropolitan area". The heavy ash fall will cause the serious disaster of course, but well developed area also suffered heavy economical damage by even a thin deposit of volcanic ash. Around five hundred distribution maps of the volcanic ash fall deposits in Japan in these three hundred thousand years were collected. The first work is to redraw the isopach map completely for each unit, because major of the isopach map in the literature were not perfect in shape. The redrawing for each contour line was carried out mathematically to extend each semicircular curve to make a close circle automatically. The redrawn isopachs were reserved as a digital data and the thickness of the deposit between each contour line for around each one kilometer mesh, which is authorized by the third Digital National Land Information system in Japan, were calculated by logarithmical proportional allotment. The worked area was from 24 to 46 degree in the north latitude and from 123 to 149 degree in the east longitude. The name of the volcano, unit name and its alphabetical abbreviation, age of the eruption, and the references, of each ash fall unit were summarized as a data base for each mesh. So it is possible to show the thickness of each ash fall unit for each one kilometer mesh. For example Haneda airport and Narita airport were estimated to be suffered the 8.7 and 3.2 centimeters ash fall from Fuji volcano in 1707 respectively. And also it is easy to find the ash fall disaster history for anywhere and any municipality, cities and towns, which number is around two thousand, in Japan. For example the municipal office building of the Tokyo Metropolitan in Shinjuku has been suffered three, five, and seventeen times air fall ash in these one thousand, ten thousand, and a hundred thousand years, respectively, and the thickness of the deposit for each periods are also able to be shown using the data base.

Petrographic Properties of Visible Tephra Layers in SG93 and SG06 Drill Core Samples from Lake Suigetsu, Central Japan

“…Layer B-22-03 can be correlated with the Daisen⊖Sekigane pumice (DSP; Machida and Arai, 1979) . Suto et al (2007) estimated the age of DSP at 80⊖55 ka from its stratigraphic position.…”

Probabilistic assessment of tephra fall hazards in Japan using a tephra fall distribution database

“…Tephra falls are a potential hazard that can damage house roofs, transportation infrastructure, and electrical facilities, even in areas that are far from volcanoes (Wilson et al, 2014). Probabilistic methods have been increasingly used to evaluate tephra fall hazards through both computational techniques (Bonadonna et al, 2005;Magill et al, 2006;Marzocchi et al, 2010;Jenkins et al, 2012a, b;Miller et al, 2016) and the evaluation of geological records (Suto et al, 2007). Computational tephra fall models (e.g., TEPHRA2: Conner et al, 2001;FALL3D: Folch et al, 2009) are coupled with wind pro le data for individual eruptions (e.g., Bonadonna et al, 2005) and regional long-term eruptions (Bear-Crozier et al, 2016;Jenkins et al, 2018).…”

“…However, evaluating the accuracy of calculations of these computational studies is di cult. Long-term tephra fall records have also been used for regional (Suto et al, 2007;Simpson et al, 2011) and local (Yamano et al, 2018) tephra fall hazard evaluations. Geological records of tephra fall events incorporate multiple factors affecting the probabilistic variability of the corresponding hazards, including the eruptive history of the source volcanoes.…”

“…Using this information, it is possible to evaluate regional, longterm probabilistic volcanic hazards in Japan. Suto et al (2007) evaluated volcanic tephra fall hazards by compiling and digitizing the data of Machida and Arai (2003), along with other isopach maps published before 2003. In addition to compiling the tephra fall distribution database, those authors determined the cumulative thickness of tephra falls from maps and obtained the maximum and minimum thicknesses at each city and town in Japan for the past 1000, 10,000, and 100,000 year.…”

“…In addition to compiling the tephra fall distribution database, those authors determined the cumulative thickness of tephra falls from maps and obtained the maximum and minimum thicknesses at each city and town in Japan for the past 1000, 10,000, and 100,000 year. However, the database of Suto et al (2007) cannot be applied to directly calculate hazard curves because the isopach contours are provided in PDF format instead of shape le format. To evaluate regional tephra fall hazards, we calculated annual exceedance probabilities (AEPs;Jenkins et al, 2018) using Probabilistic Volcanic Ash fall Hazard Assessment (PVAHA; Stirling and Wilson, 2002).…”