Numerical simulation of the landslide-induced tsunami of 1988 on Vulcano Island, Italy

On 20 April 1988 a landslide of approximately 200,000 m(3) occurred on the northeastern flank of the volcano La Fossa on the island of Vulcano. The la ndslide fell into the sea, producing a small tsunami in the bay between Pun te Nere and Punta Luccia that was observed locally in the neighbouring harb our called Porto Levante. The slide occurred during a period of unrest at t he volcano that was monitored very accurately. The study of this event is c omposed of two parts, the simulation of the landslide and the simulation of the ensuing tsunami; the former is studied by means of a Lagrangian-type n umerical model in which the landslide is seen as a multibody system, an ens emble of material-deforming blocks interacting together during their motion ; the latter is simulated according to the Eulerian view by solving the sha llow-water approximation to Navier-Stokes equations of fluid dynamics, with the incorporation of a forcing term depending on the slide motion. Technic ally, the slide evolution is computed first, and this result is then used t o evaluate the excitation term of the hydraulic equations and to calculate the tsunami propagation. Computed wave fronts radiate both toward the open sea, with rapid amplitude decay, and along the shore, in the form of edge w aves that lose energy slowly. Comparison between model outputs and observat ions can be carried out only in a qualitative way owing to the absence of t ide-gauge records, and results are satisfactory.