Combining long- and short-term probabilistic volcanic hazard assessment with cost-benefit analysis to support decision making in a volcanic crisis from the Auckland Volcanic Field,New Zealand |
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Authors: | Laura Sandri Gill Jolly Jan Lindsay Tracy Howe Warner Marzocchi |
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Institution: | (1) Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, via D. Creti, 12, 40128 Bologna, Italy;(2) GNS Science, Wairakei Research Centre, Taupo, New Zealand;(3) Institute of Earth Science and Engineering, The University of Auckland, Auckland, New Zealand;(4) School of Environment, The University of Auckland, Auckland, New Zealand;(5) Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma 1 Sismologia e Tettonofisica, via di Vigna Murata 605, 00143 Roma, Italy |
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Abstract: | By using BET_VH, we propose a quantitative probabilistic hazard assessment for base surge impact in Auckland, New Zealand.
Base surges resulting from phreatomagmatic eruptions are among the most dangerous phenomena likely to be associated with the
initial phase of a future eruption in the Auckland Volcanic Field. The assessment is done both in the long-term and in a specific
short-term case study, i.e. the simulated pre-eruptive unrest episode during Exercise Ruaumoko, a national civil defence exercise.
The most important factors to account for are the uncertainties in the vent location (expected for a volcanic field) and in
the run-out distance of base surges. Here, we propose a statistical model of base surge run-out distance based on deposits
from past eruptions in Auckland and in analogous volcanoes. We then combine our hazard assessment with an analysis of the
costs and benefits of evacuating people (on a 1 × 1-km cell grid). In addition to stressing the practical importance of a
cost-benefit analysis in creating a bridge between volcanologists and decision makers, our study highlights some important
points. First, in the Exercise Ruaumoko application, the evacuation call seems to be required as soon as the unrest phase
is clear; additionally, the evacuation area is much larger than what is recommended in the current contingency plan. Secondly,
the evacuation area changes in size with time, due to a reduction in the uncertainty in the vent location and increase in
the probability of eruption. It is the tradeoff between these two factors that dictates which cells must be evacuated, and
when, thus determining the ultimate size and shape of the area to be evacuated. |
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