Flandoli, Franco

The Somma-Vesuvius (SV) volcano has shown in its history a large variability of eruptive styles associated with a significant spatial variability of vent locations. In particular, the vent position of large explosive eruptions showed a shift within the present SV caldera. Numerical simulations of explosive eruptions with varying vent location inside the caldera indicate a major effect on the runout and dispersal of pyroclastic density currents produced by column collapse. This work summarizes the activities that have been put forward with the aim of producing a first background (also named long-term or basal) vent opening probability map for the area of the SV caldera. These activities have been focused on three main objectives: i) the collection and critical review of key volcanological features (location of past vents, distribution of faults, etc.) that can influence the spatial distribution of future vents; ii) the development of probability density maps through the use of Gaussian kernel functions on the different volcanological datasets and iii) the weighted linear combination of the density maps of the volcanological variables to produce a background vent opening probability map where uncertainties are explicitly accounted for through expert elicitation methods. Results illustrate the different influence of the volcanological variables on the final maps, the areas at higher and lower probability of vent opening and the effects of the different elicitation methods adopted to quantify the uncertainty sources. The map represents the first step to the production of maps of the probability distribution of pyroclastic flow invasion or of ash fallout for the different eruptive scenarios to be considered in the case of a next reactivation at SV.