Abstract

Effective volcanic hazard management in regions where populations live in close proximity to persistent volcanic activity involves understanding the dynamic nature of hazards, and associated risk. Emphasis until now has been placed on identification and forecasting of the escalation phase of activity, in order to provide adequate warning of what might be to come. However, understanding eruption hiatus and post-eruption unrest hazards, or how to quantify residual hazard after the end of an eruption, is also important and often key to timely post-eruption recovery. Unfortunately, in many cases when the level of activity lessens, the hazards, although reduced, do not necessarily cease altogether. This is due to both the imprecise nature of determination of the “end” of an eruptive phase as well as to the possibility that post-eruption hazardous processes may continue to occur. An example of the latter is continued dome collapse hazard from lava domes which have ceased to grow, or sector collapse of parts of volcanic edifices, including lava dome complexes. We present a new probabilistic model for forecasting pyroclastic density currents (PDCs) from lava dome collapse that takes into account the heavy-tailed distribution of the lengths of eruptive phases, the periods of quiescence, and the forecast window of interest. In the hazard analysis, we also consider probabilistic scenario models describing the flow’s volume and initial direction. Further, with the use of statistical emulators, we combine these models with physics-based simulations of PDCs at Soufrière Hills Volcano to produce a series of probabilistic hazard maps for flow inundation over 5, 10, and 20 year periods. The development and application of this assessment approach is the first of its kind for the quantification of periods of diminished volcanic activity. As such, it offers evidence-based guidance for dome collapse hazards that can be used to inform decision-making around provisions of access and reoccupation in areas around volcanoes that are becoming less active over time.

Highlights

  • AND MOTIVATIONThe ability for communities around volcanoes to recover from volcanic unrest hinge on well-judged and timely decisions about land use, as well as access to some areas around volcanoes for reasons of work, attending personal property, and/or potential reoccupation

  • We present a new probabilistic model for forecasting pyroclastic density currents (PDCs) from lava dome collapse that takes into account the heavy-tailed distribution of the lengths of eruptive phases, the periods of quiescence, and the forecast window of interest

  • Three Possibilities probability of no PDC occurring over the time frame including t years since the last recorded PDC and s years of forecast can be broken down into three cases: (1) Eruptive activity may have ceased sometime between the last recorded PDC and time t, and we will see no PDCs through the forecast window

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Summary

Introduction

The ability for communities around volcanoes to recover from volcanic unrest hinge on well-judged and timely decisions about land use, as well as access to some areas around volcanoes for reasons of work, attending personal property, and/or potential reoccupation. Hazard assessments that account for diminishing activity, cessation in eruptive activity and/or the establishment of new post-eruption background activity levels are hard to develop given that the processes involved are poorly understood, and are necessarily characterized by high uncertainties. To our knowledge no such hazard assessments have been carried out for any eruptions so far. This work is motivated by the need for reassessing the hazards from the Soufrière Hills Volcano (SHV), Montserrat, given the extended state of quiescence of the volcano since 2010. Recent Eruptive History at Soufrière Hills Volcano

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