title: Beyond eruptive scenarios: assessing tephra fallout hazard from Neapolitan volcanoes.
abstract: Assessment of volcanic hazards is necessary for risk mitigation. Typically, hazard assessment is based on one or a few, subjectively chosen representative eruptive scenarios, which use a specific combination of eruptive sizes and intensities to represent a particular size class of eruption. While such eruptive scenarios use a range of representative members to capture a range of eruptive sizes and intensities in order to reflect a wider size class, a scenario approach neglects to account for the intrinsic variability of volcanic eruptions, and implicitly assumes that inter-class size variability (i.e. size difference between different eruptive size classes) dominates over intra-class size variability (i.e. size difference within an eruptive size class), the latter of which is treated as negligible. So far, no quantitative study has been undertaken to verify such an assumption. Here, we adopt a novel Probabilistic Volcanic Hazard Analysis (PVHA) strategy, which accounts for intrinsic eruptive variabilities, to quantify the tephra fallout hazard in the Campania area. We compare the results of the new probabilistic approach with the classical scenario approach. The results allow for determining whether a simplified scenario approach can be considered valid, and for quantifying the bias which arises when full variability is not accounted for.
authors.affiliation: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, Bologna, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Sandri
authors.affiliation: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, Bologna, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Costa
authors.affiliation: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, Bologna, Italy.
authors.forename: Jacopo
authors.initials: J
authors.lastname: Selva
authors.affiliation: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma1, Roma, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Tonini
authors.affiliation: Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Napoli, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Macedonio
authors.affiliation: Barcelona Supercomputing Centre, Barcelona, Spain.
authors.forename: Arnau
authors.initials: A
authors.lastname: Folch
authors.affiliation: Università di Bari, Dipartimento di Scienze della Terra e Geoambientali, Bari, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Sulpizio