IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

3W_4C-P1

Date/Time: July 23 Poster

Space-time Analysis of Volcanic Eruptions and Disasters in Japan for the Past 2,000
Years
Yoichi Nakamura, Yuhtaro Ito, Masato Tazawa, Mika Suzuki
Utsunomiya University, Japan
E-mail: ynakamu@cc.utsunomiya-u.ac.jp

Historic records of volcanic activities and disasters provide very useful lessons for disaster mitigation planning.
Every historic document ever recorded in Japan dealing with volcanic disaster events has presently been
re-surveyed and verified. Records have been obtained for a total of 1,162 eruptions over the past 2000 year for 110
active volcanoes. The 47 active volcanoes newly designated for constant monitoring by the Japan Meteorological
Agency (JMA, 2011) account for 87% of all the eruptions. By reviewing documentation and referring to publisheddata, values of the Volcanic Explosivity Index (VEI) for approximately 90% of the eruptions recorded could beevaluated. VEI 1 and 0 eruptions were recorded only during the most recent 100 and 50 years, respectively. The
numbers of VEI 2 and 3 are mostly distributed over the past 500 years, with VEI 3 numbering the highest. Presentresults for the past 2000 years in Japan are generally similar in tendency to the world data for the past 10,000 years
reported by the Smithsonian Institution (2010). However, there have been no VEI 6 and 7 eruptions recorded inJapan.
Using the frequency-distribution analyses for eruptions as a function of VEI value, we have obtained the averagefrequency for each level of VEI. VEI 5 eruptions occur approximately once every 180 years, and VEI 4 eruptions
occur once every 50 years with some fluctuations. VEI 3 and VEI 2 eruptions occur approximately once every18
years and 4 years, respectively, but with somewhat larger fluctuations. After the space analysis, we obtained aregional view of volcanism in Japan. Kyushu is the most volcanic active area and after Kyushu, Kanto-Chubu,Izu-Mariana, Hokkaido, and Tohoku, in that order. However, larger VEI 4 and 5 eruptions tend to occur in Hokkaido.
After the results were summed up by numbers of casualties, human and physical damages due to volcanic
disasters, excluding deaths not directly related to the eruptions, e.g.

starvations or epidemics, there wereapproximately 20,000 victims over the past 2,000 years. Over 80% of the deaths were due to volcanic tsunami,
followed by deaths from lahars, including mudflows or debris flows, pyroclastic falls, debris avalanches, andpyroclastic flows. The highest number of victims per an eruption was due to volcanic tsunami and debris avalanche,
although these are very infrequent.
After performing present space-time analyses for eruptions and volcanic disasters over the past 2000 years
in Japan, specific and available data could be obtained and useful information-resources for volcanic disastermitigation could be provided. We expect local decision-makers, administrative officials of disaster mitigation
organizations and academic researchers to use these present results effectively to propose robust counter-measurestrategies to implement when future volcanic events occur.

©IAVCEI 2013 Scientific Assembly. All rights reserved.

1124