Multiscale impact assessment of massive ash fallout from a large eruption: What may happen if Sakurajima Taisho eruption occurs in contemporary Japan?

The 1914 eruption of Sakurajima (the Taisho eruption) caused catastrophic consequences by releasing enormous volcanic ash to Japan’s atmosphere, affecting both proximal and distal regions. As volcanic ash is a complex hazard that can cause damage to critical infrastructure and disrupt socio-economic activities, impacts from such an eruption in contemporary Japan will be more severe than in 1914. Despite records of past large eruptions at Sakurajima and evidence of associated threat, there are no comprehensive studies addressing the full extent of volcanic ash hazards, particularly in distal areas. To fill the gaps in current knowledge, this study presents the multiscale impacts assessment of volcanic ash hazards to contemporary Japan, using the Taisho eruption case, encompassing the physical and socio-economic impacts under both the general weather patterns and extreme weather events. This study incorporates an ash dispersal database generated using One Eruption Scenario (OES) approach which contains tens of thousands of individual eruptive episodes under various weather regimes. We then estimate the probability distributions of ashfall accumulation and overlay them on assets maps in contemporary Japan to assess potential disruption in transportation, service interruptions, damage to infrastructure, and human casualties. This study found that under typical weather, massive ashfall from a large eruption in Sakurajima volcano can disrupt and damage multiple critical infrastructure, such as airports, roads, power networks, and buildings at a local through national level, potentially causing significant economic losses and casualties. Under extreme weather when volcanic ash dispersal widens and intensifies, we found greater overall impacts due to the escalation of initial damage and addition of secondary hazards. The compounded effects of extreme weather and volcanic eruptions demands a re-evaluation of structural resilience and emergency preparedness, particularly in vulnerable regions, as part of integrated disaster management strategies.

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