Issues of prolonged volcanic eruption disaster for revival

Volcanic disasters have been protracted after an eruption. Responding to prolonged disasters after an eruption is an important for coexistence with volcanoes. The purpose of this study is to investigate the relationship between the duration of the disaster after the eruption and the revival, and to clarify the issues for the revival of the volcanic disaster. Histogram of eruption duration based on the global eruption database for the last 100 years shows that 90% are within 2 years. On the other hand, the disaster duration after the eruption of Volcanic Explosivity Index (VEI) 4 or higher was 50 to 100 years based on satellite images. The reason for the continued disaster is mainly the flooding of rivers due to deforestation and rising riverbeds. While there are many volcanoes that continue to erupt in Japan, in the past 100 years, tourism, geoparks, and the agriculture and livestock industry at the foot of the mountain have developed, and in the case of VEI 3 class, they coexist with volcanoes. In the case of VEI 4-5 class, there are cases where the disaster has continued for more than 100 years after the eruption, and there are cases where it does not return to before the eruption even after the revival. These results indicate that the important issue for revival is the response to the continuation of disasters after the eruption of VEI 4 or higher. In recent years, especially in Japan, there is little experience of large-scale eruptions of VEI 4 or higher, and it is the key to disaster mitigation to spread the understanding of infrequent large-scale eruptions to the public. In some cases, the duration of a disaster exceeds 100 years, so It is important to consider measures for medium- to long-term risk diversification and disaster mitigation in advance, including utilizing the benefits of volcanoes.