A probabilistic approach to hazard mapping based on computer simulations. An example for lava flows at Mount Etna

Determining sectors that could be affected by lava flows in volcanic areas is essential for risk mitigation purposes. Traditionally, when adopting methods based on probabilistic numerical simulations, the hazard is assessed by analysing a huge set of simulations of hypothetical events, each characterized by a distinct probability of occurrence based on statistics of historical events. If lateral or eccentric eruptions are also taken into account, simulated lava flows usually start from the nodes of regular grids of potential vents, uniformly covering the study area. In this study, an alternative approach to evaluate flow-type hazard, based on a non-uniform grid of potential vents, is proposed. The method takes into account expected changes in the topographic context due to successive lava-flow bodies, and allows to obtain more detailed maps for the most exposed areas, besides significantly reducing the computational efforts. The approach has been tested to evaluate lava-flow hazard at Mt Etna (Eastern Sicily, Southern Italy), and a preliminary analysis has been performed to investigate the behaviour of the adopted technique with respect to the number of performed sets of simulations to better understanding its predictive capability.