A probabilistic mitigation system by eruptive event-trees, eruption-scenarios and risk assessments, evaluated by volcanic disasters records during past 2,000-year in Japan

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A database of volcanic hazard maps in Japan was worked out. Current version includes 160 maps and handbooks published for 40 of the 110 active volcanoes. Records dealing with volcanic disasters have been obtained for a total of 1,162 eruptions over the past 2,000 years. There were approximately 20,000 victims and over 80% of the deaths were due to volcanic tsunami, followed by deaths from lahars, including mudflows or debris flows, pyroclastic falls, debris avalanches, and pyroclastic flows. Frequency-distribution analyses for eruptions show the average frequency for each of VEI. The VEI 5 eruptions occur once every 180 years, and VEI 4 occur once every 50 years. VEI 3 and VEI 2 eruptions occur once every18 years and 4 years. We expect local administrative officials to use present probabilistic mitigation system implemented with risk assessments, eruption event-trees and scenarios results to propose robust counter-measure strategies to implement when future volcanic events occur.