Numerical Modelling of a Landslide-generated Tsunami: The 1979 Nice Event

Abstract

—On the 16th of October 1979, a part of the Nice new harbour extension, close to the Nice international airport (French Riviera), slumped into the Mediterranean Sea during landfilling operations. A submarine slide with initial volume close to seashore of about 10 millions m³, which could have evolved later into an avalanche, was followed by a small tsunami, noticed by several witnesses in the “Baie des Anges.” The maximum tsunami effects were observed 10 km from the slide location near Antibes city, which was inundated. Previous analyses used rough approximate methods and produced models which did not conveniently fit data. In this paper, both the slide and the generated water waves are numerically simulated on the basis of the shallow water approximation. The landslide is assimilated to a heavy Newtonian homogeneous fluid downslope under gravity. Water waves are generated by sea-bottom displacements induced by the landslide. Taking into account a very accurate multibeam bathymetric map, the Nice slide of 10 millions m³ is simulated by this model. The numerical results are generally consistent with the observed hydraulic local effects in front of the Nice airport, however they are not in agreement in the far field. A larger and deeper landslide 2 km off Nice airport is tested to quantitatively study the effects of the landslide volume on water waves generation.