SEFASILS cruise (Seismic Exploration of Faults And Structures In the Ligurian Sea) aims prioritarily at studying the crustal structure of the North Ligurian margin, and in particular, the geometry at depth of the fault system that crops out at the continental slope's toe between Nice and the Gulf of Genoa. This faulting is responsible for the margin uplift - particularly pronounced towards East, on the Imperia promontory - and studies point towards its activation during the 1887 Ligurian earthquake (6.9 assessed magnitude, important damage from Menton to Genoa, 2-m high tsunami, more than 600 fatalities). Besides, the nature and structure of the crust formed during the Oligo-Miocene opening of the oceanic Ligurian basin remain enigmatic due to its being burried below a several km-thick sedimentary cover that includes a thick, mobile Messinian salt-bearing unit, whose surficial tectonic expression can be mixed up with motions of deeper origin. This basin is indeed characterized by an intra-oceanic seismic activity in its northern part (some events exceeding a magnitude of 6 have been reported there), occurring along faults that are yet to be identified.

In order to answer those questions, we perform the acquisition of dense refaction seismic data (lines of OBSs with 1.5 to 3 km spacing), as well as deep multichannel reflection seismic data. Three large profiles crossing the northern margin and a large part of the basin are targeted, one of them extending all the way to the conjugate Corsican margin. A fourth profile along the northern margin, in seismic reflection only, must allow a correlation, as well as to study the lateral variability of structures beneath the margin.

Some difficulties were encountered in obtaining permits for Italien waters implying lengthy delays. The cruise therefore had to be splitted in two legs, the first one only in French and Monaco waters.

Some leading edge processing methods are targeted with these data sets: slope tomography, stereotomography, prestack depth migration and full waveform inversion. All these tools have been developed in Geoazur along the last 15 years.