Hazard assessment of explosive volcanism at Somma‐Vesuvius

A probabilistic approach based on the available volcanological data on past
Somma‐Vesuvius eruptions has been developed to produce hazard‐zone maps for fallout,
pyroclastic density currents (PDCs), and secondary mass flows by using numerical
simulations. The hazard maps have been incorporated in a GIS, making them accessible to
casual and expert users for risk mitigation and education management. The results allowed
us to explore the hazard related to different scenarios from all possible eruptions,
ranked according to volcanic explosivity index (VEI) class, in the Vesuvius area and its
surroundings including Naples. Particularly, eruptions with VEI ≤ 3 would produce a
fallout hazard within about 10 km mostly east of the volcano and a PDC hazard within
about 2 km from the crater. Large‐scale events (4 ≤ VEI ≤ 5) would produce a fallout
hazard up to 80 km from the vent and a PDC hazard at distances exceeding 15 km.
Particularly, the territory northwest of Vesuvius, including metropolitan Naples, featuring
a low hazard level for fallout accumulation, is exposed to PDCs also consistent with field
evidence and archeological findings. Both volcano flanks and surrounding plains, hills,
and mountains are exposed to a moderate–high level of hazard for the passage of
secondary mass flows. With the present level of uncertainty in forecasting future eruption
type and size on the basis of statistical analysis as well as precursory activity, our results
indicate that the reference scenario in the emergency plan should carefully match the
worst‐case VEI 5 probabilistic scenario.

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