Structured elicitation of expert judgement in real-time eruption scenarios

Abstract

Formalised elicitation of expert judgements has been used to help tackle several problematic societal issues, including volcanic crises and pandemic threats. We present an expert elicitation exercise for Piton de la Fournaise volcano, La Réunion island, held remotely in April 2021. This involved 28 experts from nine countries who considered a hypothetical effusive eruption crisis involving a new vent opening in a high-risk area. The tele-elicitation presented several challenges, but is a promising and workable option for application to future volcanic crises. Our exercise considered an “uncommon” eruptive scenario with a vent outside the present caldera and within inhabited areas, and provided uncertainty ranges for several hazard-related questions for such a scenario (e.g. probability of eruption within a defined timeframe; elapsed time until lava flow reaches a critical location, and other hazard management issues). Our exercise indicated that such a scenario would probably present very different characteristics compared to recent eruptions, and that it is fundamental to include well-prepared expert elicitations in updated civil protection evacuation plans to improve disaster response procedures.

Interdisciplinary research in hazards and disaster risk

“…Human geographical analyses of the science-policy processes further reveal social forms of uncertainty that may or may not be readily quantifiable. In expert judgement exercises, for example, experts may make an estimate of their own uncertainty (Bamber and Aspinall 2013;Cooke 2008;Tadini et al 2022)but there are also more indeterminate sources of social anxiety within a decisionmaking group, between scientists and officials and other groups toorequiring a more substantial framework for understanding uncertainty in the context of 'wicked problems' (Donovan 2019;Stirling 2007;Sword-Daniels et al 2016;Wynne 1992). Additionally, the use of belief-based probabilistic methods raises challenges for some scientists, who regard such methods as unscientific due to the heavy reliance on subjective judgements (Castanos and Lomnitz 2002;Donovan, Oppenheimer and Bravo 2012b;O'Hagan 2008).…”

Volcanic crisis management supported by near real-time lava flow hazard assessment at Piton de la Fournaise, La Réunion

“…To illustrate our operational near real-time protocol, we present the response to three eruptive events as case studies, these being the eruptions of 25-27 October, 2019 (an eruption that threatened the road belt), 10-16 February, 2020 (an eruption that started only 20 minutes after the start of the seismic crisis), and 7-8 December, 2020 (when the response protocol was triggered in a record time after the eruption onset). Additionally, we provide a hypothetical case study of an eruption outside of the main caldera in an inhabited area, based on the scenario proposed in Tadini et al [2022]. For each case study we describe the eruption timeline (given in the local time zone, i.e.…”

“…Hors Enclos eruption) in an inhabited area. This scenario is based on the expert elicitation exercise proposed by Tadini et al [2022]. We chose this case to test our protocol for an eruption that could potentially impact population in inhabited areas.…”

“…A vent opening in a populated zone requires particularly rapid response, and our previous case study in Section 4.3 (7-8 December, 2020 eruption) shows that, if all actors are together on site, such map can be produced and sent to EMZPCOI at best within 10 minutes of the communication of the vent location. In the case of the expert elicitation exercise proposed by [Tadini et al 2022] only the path of steepest descent was provided to the experts and this was about 6 hours after the start of the eruption because it included reports from initial field reconnaissance by OVPF-IPGP staff, confirming vent locations and flow front locations. Here we show the first hazard map that we could have been produced following our protocol (Figure 7A).…”

Assessing minimum pyroclastic density current mass to impact critical infrastructures: example from Aso caldera (Japan)

“…Note that volume is not considered an input parameter but it is varied to calculate the probability of any volume chosen in a wide range to reach the distance of each marker site. For judgment aggregation, we implemented the equal weights combination rule Tadini et al, 2017Tadini et al, , 2021bTadini et al, , 2022b. We did not apply performance-based scores because of the relatively small number of experts participating and because the overheads and time demands involved in implementing a formal elicitation protocol were not warranted in this case.…”