MAPPING THE TEPHRA FALLOUT RISK - AN EXAMPLE FROM VESUVIUS, ITALY

THE goal of evaluating the risks related to the reactivation of a quiescent volcano requires the reconstructions of the eruptive history of the volcano, the construction therefrom of a behavioural model of the volcano so as to define the 'maximum expected event9 and the subsequent quantitative models allowing reliable simulation of such an event to be set up and hazard and risk maps to be developed. We have followed this approach to infer the size and character of the explosive eruption of Vesuvius to be expected after a 45-year rest period1,2, and we used a numerical model, tested on the recent Mount St Helens eruption and the Vesuvius eruption in AD 79 3,4, to simulate tephra transport and fallout. By combining the fallout model with a statistical analysis of the wind regime and with the density of urban settlement, we were able to assess quantitatively the tephra fallout risk. © 1990 Nature Publishing Group.