Structured Elicitation of Expert Judgment for Probabilistic Hazard and Risk Assessment in Volcanic Eruptions

When a potentially dangerous volcano becomes restless, civil authorities invariably turn to scientific specialists to help them anticipate what the volcano will do next, and to provide them with guidance as to the likely threats. Although it is usually possible to discern the earliest signs of unrest, the science of forecasting the course and timing of eruptions remains inexact. In this chapter, recent volcanic crises in the Eastern Caribbean are recounted in order to trace the emergence of a need for volcanologists to formalise the way they present scientific advice in such circumstances. The conversation then moves on to the concepts and principles of eliciting expert opinion, and structured elicitation within a mathematical framework, before describing in more detail a specific performance-based procedure for eliciting opinions that relies on proper scoring rules. Ways in which this procedure and its scoring basis have been adapted for use in the recent Montserrat volcanic crisis are discussed, and the purposes for which the formalized procedure has been used during that eruption, in application to hazard and risk management, are described. Finally, a few general observations are offered in respect of the benefits and limitations of using a