Landslide tsunami vulnerability in the Ligurian Sea: case study of the 1979 October 16 Nice international airport submarine landslide and of identified geological mass failures

Abstract

International audienceThe Ligurian sea, at the France–Italy boarder of the Mediterranean Sea, has experienced in the past numerous submarine landslides within its very near continental slope, the continental shelf being very narrow. The most recent occurred on the 1979 October 16 near Nice international airport and generated tsunami waves of order 3 m of amplitude in some specific locations. More ancient landslides are also easily identified through bathymetric surveys of the seafloor. For the 1979 event we propose two distinct tsunamigenic landslides based on identified scars observable on the seafloor. The first one corresponds to the volume Vol1 that slid at the airport (in shallow water) while the second one corresponds to the more substantial volume Vol2 that has been localized at the slope. Former studies indicate that only the combination of the two slides may explain the event. We complement these studies by asserting that when the two slides are taken separately, they already explain a significant (although not a total) part of the event: Vol1 explains partly the tsunami observations in the vicinity of the airport while Vol2 contributes to explain the ones away from the area, in particular at Antibes where the highest wave has been observed. The modelling effort is then extended to evaluate the tsunamigenesis of selected (but representative) former landslides having a clear scar signature. The vulnerability of the area to landslide-triggered tsunami is then proposed to discussion along with possible mechanisms that can be responsible for local wave amplification

Cone penetration testing to assess slope stability in the 1979 Nice landslide area (Ligurian Margin, SE France)

“…It is characterized by deeply-incised canyons generated by the Var and Paillon rivers with side-wall gradients up to 27° (Fig. 1b, Pautot 1981, Klaucke et al 2000, Ioualalen et al 2010, and a large number of smaller steep-sided valleys, eroded surfaces, scars, ridges and gullies ( Fig. 1b; see also Migeon et al 2012 for detailed AUV bathymetry images).…”

Frequency and triggering of small-scale submarine landslides on decadal timescales: Analysis of 4D bathymetric data from the continental slope offshore Nice (France)

“…Much attention has been given to a submarine-failure event on 16 October 1979 (Gennesseaux et al, 1980;Mulder et al, 1997). The -1979 failure‖ was responsible both for the destruction of the new harbor-airport complex of Nice and for the triggering of a 2-3-m high local tsunami (Gennesseaux et al, 1980;Ioualalen et al, 2010). Although the causes are still debated, the main factor is thought to be an anthropogenic trigger related to infilling operations and loading of the harbour embankment above under-consolidated fine-grained plume deposits of the upper slope (Dan et al, 2007).…”

Soft sediment deformation in the shallow submarine slope off Nice (France) as a result of a variably charged Pliocene aquifer and mass wasting processes

“…It is characterised by deeply-incised canyons generated by the Var and Paillon rivers with side-wall gradients up to 27°( Fig. 2A, Pautot, 1981;Klaucke et al, 2000;Ioualalen et al, 2010), and a large number of smaller steep-sided valleys, eroded surfaces, scars, ridges and gullies (Figs. 1, 2A; see also Migeon et al, 2012 for detailed AUV bathymetry images).…”

“…Based on bathymetry data the volume of failed material was estimated~0.0022 km 3 near the airport and~0.0062 km 3 in the mid-slope and displaced sufficient water to generate a tsunami wave of 2-3 m (Ioualalen et al, 2010). The resulting debris flow cut two submarine cables (ca.…”