A Probabilistic Approach to Risk Mapping for Mt. Etna

We evaluate susceptibility to lava flows on Mt. Etna based on specially designed die-toss experiments using probabilities for type, time and place of activation from the volcano's 400-year recorded history and current studies on its known fractures and fissures. The types of activations were forcast using a table of probabilities for events, typed by duration and volume of ejecta. Lengths of time were represented by the number of activations to expect within a given time-frame, calculated assuming Poisson-distributed inter-arrival times for activations. Locations of future activations were forecast with a probability distribution function for activation probabilities. Most likely scenarios for risk and resulting topography were generated for Etna's next activation (average 7.76 years), the next 25, 50 and 100 years. Forecasts for areas most likely affected are in good agreement with previous risk studies made. Forecasts for risks of lava invasions, as well as future topographies might be a first. Threats to lifelines are also discussed.