Shigeru Suto, Takayuki Inomata, Hisashi Sasaki and Sakae Mukoyama (2007) Data base of the volcanic ash fall distribution map of Japan. Bull. Geol. Surv. Japan, vol. 58(9/10), p.261-321, 8 figs, 2 tables, 1 appendix fig, 2 appendix tables. 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. Keywords: volcanic ash fall, ash fall disaster, ash fall data base, isopach map, Japanese volcano, Fuji volcano
Table 1 List of the volcano which was described in this report with the number of the ash fall unit.
Fig. 1 Locality of the volcanoes which were described in this report.
Fig. 2 Schematic figures to show how to complete the isopach.
a) c) b) d)
e) f) Fig. 3 Example of the distribution map of the each ash fall unit. a) SBA, Miyakejima, b) Osawa unit, Nasudake, c) Chanai group, Mashu caldera, d) Akagi Namekawa 1, Akagi, e) Kuccharo Hahoro, Kusharo caldera, f) Aira Tn, Aira caldera.
a) c) b) Fig. 4 Total thickness of the volcanic ash fall. a) in the last one thousand years, b) in the last ten thousand years and c) in the last one hundred thousand years.
a) c) b) Fig. 5 Total number of the volcanic ash fall unit. a) in the last one thousand years, b) in the last ten thousand years and c) in the last one hundred thousand years.
a) c) b) Fig. 6 Total thickness of the volcanic ash fall, which eruption center were fixed on the same place. a) in the last one thousand years, b) in the last ten thousand years, and c) in the last one hundred thousand years.
a) c) Fig. 7 Total number of the volcanic ash fall unit, which eruption center was fixed on the same place. a) in the last one thousand years, b) in the last ten thousand years, and c) in the last one hundred thousand years.
Table 2 Volcanic ash fall data at the Tokyo Metropolitan Government Office. Fig. 8 Relation between the number of the ash fall unit and the eruption age.
Appendix fig. 1 Distribution map of the each ash fall unit. Readable on the website, http://www.gsj.jp/pub/bull_new/vol_58/58_09/58_09_01_01-15.pdf.
Appendix table 1 List of the volcanic ash fall unit.
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Appendix table 2 Data base of the ash fall deposit for each municipality. Thickness is shown in centimeter.
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