Modeling of the 1783 tsunami event in Scilla generated by earthquake and landslide

In 1783 began what has gone down in history as the great seismic crisis in Calabria, during which two major earthquakes occurred which affected the Calabrian ridge from the Strait to the north. Between 6th and 7th February in Scilla there was the tsunami that caused the greatest number of victims in Italy: 1500 people. The mechanism that triggered the tsunami was the detachment of a ridge of rock due to the violent earthquake that affected the area; this detachment caused a subaerial landslide which , by sliding, then deposited on the seabed a few kilometers from the coast, immediately generating the tsunami event. The generation mechanism was, therefore, by evaluating temporally what happened, the submarine deposit of the landslide that broke off the coast. During these years some studies have been carried out, by means of numerical modeling, aimed at interpreting and evaluating the extent of the event; the understanding and relative modeling capacity of an event of this magnitude is fundamental for future risk assessments on the Calabrian coasts that could be affected by these phenomena. The objective of the research is to perform numerical simulations with state-of-art tsunami generation and propagation models, using the best possible bathymetric and topographic data and the historical data to compare the goodness of the results. In this way we obtain the validation of a model that can be used to simulate possible events of this magnitude on the Calabrian coasts and therefore be able to have a reliable tsunami early warning system; it has also the advantage of perfectly combining computational burdens and goodness of results. Regarding the hypothesis made in this study on the shape and the sliding time of the landslide necessary for the simulation, reference was made to models and simulations developed by other authors, in particular Mazzanti and Bozzano (2008). Once the landslide and its movement has been hypothesized, it was inserted in the model and the event was simulated; the data was compared with the historical data deriving from a collection of testimonies of survivors. A numerical model developed by Bellotti (2008) an based on the mild-slope equation is applied to reproduce the propagation of small-amplitude transient waves. The model make use of the Fourier Transform to convert the time-dependent hyperbolic equation into a set of elliptic equations in the frequency domain. This application is presented to show the applicability of the present approach to real life scenarios; at the end it is discussed how this model could be applied as support to a tsunami early warning system in Calabrian coasts.