Mitigation Systems by Hazard Maps, Mitigation Plans, and Risk Analyses Regarding Volcanic Disasters in Japan

More than 60 volcanic hazard maps have been published on 38 of Japan’s 108 active volcanoes. Two maps were published before 1990, 17 after the 1991 eruptions of Unzen, and 19 after the 2000 eruptions of Usuzan and Miyakejima. Large eruptions greatly increase concern over volcanic hazards. The earlier academic maps themselves have changed from being specialist-oriented to being designed to be more easily understood with volcanic terms clearly explained. This is especially true of revised maps. The 1961 Disaster Countermeasures Basic Act directs that local disaster management plans be promoted by local governments, but only 5 of the local governments in the 25 prefectures neighboring on active volcanoes have set up established specific volcano-oriented antidisaster programs. Others mention volcanic disaster measures in the context of general or storm and flood disaster measures, and another six make no mention of particular measures for volcanic disasters. This lack of concern is somewhat understandably related to budget policies, but real-time hazard maps with probability tree algorithms for forecasting volcanic events are needed to manage potential volcanic disasters effectively. For this purpose, volcanic disaster measures with volcanic risk, or threat analyses assessments must be completed, but no local governments have yet conducted assessments of volcanic risk analyses. Whatever and however complex the reasons, local governments should, cooperating with volcanologists and supported by local residents, take action before an eruption next occurs.