"Isola di Stromboli: Carta del Rischio da Lanci Balistici - Aree a massima vulnerabilita'".

At Stromboli, the ballistic impacts of volcanic ejecta represent for short to medium term the major hazardous volcanic events for the two settlements of the island (Stromboli and Ginostra villages). This general statement is actually useless for practical purposes on risk analyses, accounting that the strombolian activity of this volcano widely ranges from discrete, mild explosions with countinuous venting of gas (normal regime) to violent bursting episodes (violent regime), and both regimes are aperiodically punctuated by more dangerous, scaled up energetic explosive pulses with expulsion of dense lithics (paroxysmal regime). As the quantitative characterization of this three regimes represents the starting point for a reliable risk evalutation at Stromboli, we constrained in the present work the initial velocities of the ejecta (scoria, bombs, dense blocks) at the takeoff point in the ranges of [40 m/s ÷ 60 m/s], [70 m/s ÷ 100 m/s], [120m/s ÷ 200 m/s] respectively for the normal, violent ad paroxysmal regime by numerical modeling of the ballistic trajectories on air. The resulting solutions also indicate that, in the case of violent or paroxysmal activity, wind velocity and direction are important warning elements that should be considered by the Civil Protection Autority in designing of evacuation plains and fulfilment of alarm level scales: data analysis including tailwinds up to 20 - 25 m/s (wind velocity not uncommon at the Stromboli Island, Beaufort number 9) points out an increase of hazard due to ballistic impacts during the paroxysmal regime for both settlements with respect to tail-winds = 0 m/s conditions, as well as the appreciable hazard level for the Ginostra village even during episodes of violent strombolian regime.