Magic2 Methodology used for the identification of tsunami landslides. (DCAT-AP IT)

The estimation of the tsunamigenic potential associated with events of gravitative instability in the underwater environment was made through the use of numerical models based on morphometric parameters proposed in the scientific literature by Grilli & Watts (1999), Watts (2000), Watts et al. (2003). In particular, this approach involves estimating the maximum height of the tsunami wave generated on the centre of gravity of an underwater landslide based on some empirical relationships, derived from fluid-dynamic simulations in the laboratory and numerical modeling. The assumptions underlying these models are as follows: a) the geometry of the underwater landslide is represented by a semi-ellipse translating along an inclined plane, b) the mass center of the landslide is identified through an analytical solution of the motion equation, c) the internal deformation of the displacement mass is neglected, as it appears to have a limited influence on the amplitude of the tsunami (Watts et al., 2003). Two different formulations have been proposed to estimate the maximum wavelength of an underwater landslide: 1) one is valid for translational landslides, which are most affected by the resistance exerted by the surrounding fluid during flowing and 2) the other is valid for rotational landslides, where there is mainly a strong basal friction. Given the fact that it is often difficult to distinguish the two types of landslides only on a morphological basis, in this study all detachment niches were considered as translational, even in accordance with the broad scientific literature, which shows a clear predominance of translational underwater landslides along the different continental margins. The perimeter of areas susceptible to potentially tsunamigenic underwater landslides is based mainly on the results of the previous activity 3.2 “Cartography related to the main landslides of the Italian seas, considered potentially tsunamigenic in their past activity”, where all those sectors of the continental margin that in the past have been potentially subject to tsunamigenic landslides have been reported. During this phase a qualitative analysis of the morpho-batimetric characteristics and the general geological structure of the marine sectors adjacent to them was carried out, in order to extend the margin areas where possible predisposing conditions and triggering the development of future processes of gravitative instability potentially tsunamigenic, in view of the fact that in the past potentially tsunami landslides occurred within these areas. It is essential to emphasise that such a perimeter will have a degree of in-depth detail and first level detail, not based on an in-depth study of the seism-stratigraphic structure of the margin, of the lithology and consistency of the seabed, of the historical and instrumental seismicity, of the structural structure of detail, studies that fall outside the possibilities and modes of the activities provided for in this Convention.