Computation of run-up heights for landslide-generated tsunami. An attempt of hazard assessment in the North Sicily continental margin

The North Sicily continental margin is a very active region located in a transitional area between the Sicilian- Maghrebian Chain to the south and the southern Tyrrhenian Sea to the north. Strong seismicity, active tectonics and volcanism, fluid escape, high sediment supply and widespread mass movements exposed this region to marine geohazards, with a potential for tsunami generation (e.g. Messina 1908, Stromboli 2004 events). In recent years, high resolution swath mapping and high resolution to high penetration seismic reflection profiles have been collected during several oceanographic cruises, in the frame of the MaGIC and CARG projects. Morphobatymetric and geoseismic analysis evidenced the main hazard elements and allowed the production of risk maps. Available data revealed that one of the most common mechanisms associated with marine geo-hazards is due to submarine mass failure processes, genetically linked to other processes active in this margin (canyon, gas venting, volcanism, tectonic structures, volcanoes, high sedimentation rate). With the aim to assess the risks linked to landslide-generated anomalous waves we selected two different sectors of the North Sicily continental margin, located in the western (Gulf of Palermo) and eastern (offshore Patti) coasts. These area were selected based on their morphologic, stratigraphic and tectonic setting and for the large amount of morphostructural elements. The working flow developed through different steps as follows: • identification and mapping of the main morphobathymetric elements affecting unstable areas; • characterization and morphometric analysis of landslide scars (ten Brink et al., 2006) selected on the base of their hazard potenzial; • computation of parameters (wavelenght, velocity, amplitude) of landslide-generated anomalous waves (Rahiman and Pettinga, 2006); • modelling tsunami runup expected by the largest failure volume, breaking on the Sicily coastline, based on Green law relations and solution of the Boussinesq equations (Choi et al., 2006). In detail, we obtained values of maximum run-up of 6.6-9.1 m for the Gulf of Palermo and 6.3-13.3 m for the Patti offshore. However the obtained values appear to be overvalued because the model foresees a precautionary scenario. Moreover the next step will be the assessment of inundation, taking into account the morphologic features of the coastal area and the roughness, land-use and urbanization of the affected areas, concerning a wider concept of risk assessment.