Modelling and numerical simulations of tsunami waves generated by landslides at Stromboli volcano (Aeolian islands, Italy)

On 30 Dec 2002, following an intense period of lava effusion activity of Stromboli volcano, a large amount of material from the "Sciara del Fuoco" collapsed and two major landslides occurred 7 minutes apart. In about 90s after the failures, the tsunami reached the north-eastern coast of the island resulting in a maximum run-up of 10 m and a maximum inland flooding distance of 100 m, injured three people and caused extensive damage to Stromboli village. Waves from the tsunami were observed throughout the Aeolian archipelago, on the island of Ustica, along the northern coasts to the south of Sicily, as well as along the coasts Tyrrhenian Sea from Calabria and Campania. The tsunamis caused damages on the island of Panarea, (about 20 km from the source).

An event like the one on 30 Dec 2002 increased the awareness that the risk from landslides and tsunamis at Stromboli was severely been underestimated and that this is a much more common hazard than believed. In the framework of the agreement between INGV and the Italian Dept of Civil Protection (DPC), a project aimed at simulating tsunami waves generated by submarine and sub-aerial landslides at the Stromboli island was funded. In this work, we present a model comparison work, carried out by INGV-Pisa in collaboration with the EDANYA group (Univ of Málaga), aimed at identifying the optimal modelling approach for tsunami hazard assessment and early warning in a volcanic context where 1) the source conditions are difficult to predict, to observe and to model; 2) the tsunamigenic source is close to the shoreline; 3) the bathymetry is extremely steep and irregular.

For this work more than 100 numerical simulations have been performed with Landslide-HYSEA and more than 40 with Multilayer-HYSEA, both with hydrostatic and non-hydrostatic approximations with one or more layers. Different grid resolutions have been tested: 5, 10, 20 and 40m. For each scenario (different volumes) and for each model we have compared: (1) The tsunami waveforms sampled at four different positions correspondent two to the buoys installed in Stromboli and two in correspondence of virtual buoys located one in front of the inhabited area in front of the port of Balordi and one in the vicinity of Strombolicchio; (2) The inundation height along the coast in the stretch that goes from Spiaggia Lunga to Porto; and (3) The execution times.