Numerical simulations of the tsunami induced by the 1627 earthquake affecting Gargano, Southern Italy

Abstract

A study of the historical tsunami that occurred on 30 July 1627 in Gargano, Apulia, southern Italy, has been conducted by performing numerical simulations based on integrating shallow water equations via a finite-element (FE) technique. The tsunami was generated by an I = XI earthquake which produced severe damage in the Gargano promontory. Macroseismic observations are not sufficient to determine, unambiguously, the epicentre and the generative fault position. In this study we have assumed a dip-slip focal mechanism which is known to be the most effective tsunami generation. Since the source location is uncertain, different simulations have been carried out assuming that the fault is placed on land (two cases) and offshore (two cases). The Adriatic basin facing the northern coast of Gargano has been covered by a triangle-based mesh, with triangle sizes adapted to the variable bathymetry, which proved to be advantageous in describing the irregular coastlines. The available historical observations concerning the tsunami are scarce and chiefly qualitative. Yet, comparing data with the results of the numerical simulations gives some important hints on the position of the genetic fault. Of all the sources studied, the one matching the observations better is the inshore fault causing the uplift of the sea block facing the Lésina lake. Accordingly, at the present stage of research, this fault can be assumed as that responsible for the 1627 earthquake and tsunami.