Rational volcanic hazard forecasts and the use of volcanic alert levels

Abstract

Volcanologists make hazard forecasts in order to contribute to volcanic risk assessments and decision-making, in areas where volcanic phenomena have the potential to impact societal assets. Present-day forecasts related to the potential occurrence of an eruption mostly take the form of alert levels, that are established by volcano scientists with the aim of communicating the state of a volcano and its possible short-term evolution. Here I analyse current alert level systems and their role in decision-making processes. I show that the use of such systems implies predictive capabilities not supported by corresponding levels of confidence in the knowledge of the volcano. Their use also implies an assumption of volcano scientist responsibility for decisions that goes beyond the expertise of the scientist, and which, in most countries, is not granted by a corresponding societal mandate. A rational volcanic hazard forecast system accepts instead the uncertain nature of volcanic processes and the consequent limited predictive capabilities; forecasts expressed as probabilities, or better as probability distributions, reflect a rational attitude by scientists and assure clear roles that reflect both expertise and societal mandate to any group involved in the management of a volcanic crisis. Exceptions where the use of volcanic alert levels may lead to efficient management are also discussed.

Towards Quantitative Volcanic Risk of Pyroclastic Density Currents: Probabilistic Hazard Curves and Maps Around Somma‐Vesuvius (Italy)

“…(e.g., Calder et al, 2015;Marzocchi & Woo, 2009). We remark, however, that the specific choice of thresholds in flow speed/depth or exceedance probability used to produce these maps, especially if the thresholds are linked to actions, should be made by decision-making agencies (e.g., Marzocchi et al, 2012;Papale, 2017).…”

Volcano observatory best practices (VOBP) workshops - a summary of findings and best-practice recommendations

“…Risks posed by volcanic eruptions continue to grow as populations near active volcanoes and air traffic over them continue to increase; however, in recent decades, enhanced technical capability of volcano observatories and their associated scientists to detect and analyze unrest and provide actionable information and eruption forecasts have reduced risk and minimized loss of life and property (Loughlin et al 2015;Auker et al 2013). This capability carries with it the responsibility to construct the best possible practices of monitoring, data interpretation, and hazard communication to support risk-mitigation decisions, such as whether and when to evacuate populations and/or restrict travel and commerce in order to save lives and property (Bazelon 1979;Miller and Jolly 2014;Papale 2017, Bretton et al 2018a.…”

“…Volcanic forecasts, expressed as probabilities, are in the form necessary for these types of cost/benefit analyses and can aid in such decision making. Consequently, it is desirable and recommended that forecasts be expressed as probabilities (Marzocchi and Woo 2007;Papale 2017), either in quantitative or qualitative terms depending on the desires and capabilities of the audience ("Probabilistic forecasting..." section).…”

Short-Term Forecasting and Detection of Explosions During the 2016–2017 Eruption of Bogoslof Volcano, Alaska

“…Unlike volcanoes that are near large populations and infrastructure, where warnings related to volcano hazards may initiate complex and costly evacuations and public concern, warnings about activity at Bogoslof led to fairly straightforward actions to ensure that aircraft would divert around any ashbearing cloud. In this case, the use of straightforward color codes and warnings was effective for managing the crisis (Papale, 2017).…”