Regional ash fall hazard II: Asia-Pacific modelling results and implications
In a companion paper (this volume), the authors propose a methodology for assessing ash fall hazard on a regional scale. In this study, the methodology is applied to the Asia-Pacific region, determining the hazard from 190 volcanoes to over one million square kilometre of urban area. Ash fall hazard is quantified for each square kilometre grid cell of urban area in terms of the annual exceedance probability (AEP), and its inverse, the average recurrence interval (ARI), for ash falls exceeding 1, 10 and 100 mm. A surrogate risk variable, the Population-Weighted Hazard Score: the product of AEP and population density, approximates the relative risk for each grid cell. Within the Asia-Pacific region, urban areas in Indonesia are found to have the highest levels of hazard and risk, while Australia has the lowest. A clear demarcation emerges between the hazard in countries close to and farther from major subduction plate boundaries, with the latter having ARIs at least 2 orders of magnitude longer for the same thickness thresholds. Countries with no volcanoes, such as North Korea and Malaysia, also face ash falls from volcanoes in neighbouring countries. Ash falls exceeding 1 mm are expected to affect more than one million people living in urban areas within the study region; in Indonesia, Japan and the Philippines, this situation could occur with ARIs less than 40 years.
KeywordsVolcanic hazard Hazard assessment Probabilistic modelling Ash dispersion Regional hazard assessment Modelling implications
The authors would like to thank Lee Siebert (Smithsonian Institution) for providing unpublished data and for helpful discussions regarding volcano type categorisation and Tony Hurst (GNS Science) for the ASHFALL source code. We also sincerely thank Costanza Bonadonna and Warner Marzocchi for providing detailed and very valuable reviews of the manuscripts and the editors of Bulletin of Volcanology for their support. This research was carried out while Susanna Jenkins was holding an International Macquarie University Research Scholarship.
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