Quantifying ash fall hazard is problematic, in part because of data limitations that make eruption characteristics uncertain but also because, given an eruption, the spatial pattern of ash dispersal is then controlled by time and altitude-varying wind conditions. Any one location may potentially be affected by ash falls from one, or a number of, volcanoes. In an attempt to deal with these uncertainties, this paper outlines a probabilistic framework for assessing ash fall hazard on a regional scale. The methodology employs stochastic simulation techniques and is based upon generic principles that could be applied to any area, but are applied here for the Asia-Pacific region. Average recurrence intervals for eruptions greater than or equal to VEI 4 were established for each of 190 volcanoes in the Region, based upon the eruption history of each volcano and, where data are lacking, the averaged eruptive behaviour of global analogous volcanoes. Eruption histories are drawn from the Smithsonian Institution’s Global Volcanism Program catalogue of Holocene events and unpublished data, with global analogues taken from volcanoes of the same type category: Caldera, Large Cone, Shield, Lava dome or Small Cone. Large numbers of plausible eruption scenarios are simulated, with spatial patterns of ash dispersal for each determined using an advection-diffusion model and local wind conditions. Key uncertainties are described by probability distributions. A companion paper describes the results obtained for the Asia-Pacific Region, with estimates of the annual probability of exceeding certain ash thicknesses summed over all eruption scenarios and volcanoes.
|Translated title of the contribution||Regional ash fall hazard I: A probabilistic assessment methodology|
|Number of pages||14|
|Journal||Bulletin of Volcanology|
|Publication status||Published - Jun 2012|