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Stefano Tinti, University of Bologna (Italy)
Fabio Trincardi, ISMAR-CNR (Italy)
Gianluca Pagnoni, University of Bologna (Italy)
Alberto Armigliato, University of Bologna (Italy)
Filippo Zaniboni, University of Bologna (Italy)
Federica Foglini, ISMAR-CNR (Italy)
Fabiano Gamberi, ISMAR-CNR (Italy)
Daniel Minisini, Eni (Italy)
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The SW Adriatic margin provides evidences of numerous sites of slope instability from the shelf edge to the slope base and along a margin stretch of about 150 km. The upper slope displays multiple and steep headscarps in compacted sedimentary units deriving from a set of Pleistocene regressive sequences with a gentle basinward-dip. On the seafloor, Gondola Slide is the most evident mass wasting deposit with large blocks, a pronounced slide scar (10 km x 2.5 km) breaching the shelf edge (about 180 m deep today but at a paleodepth of about 50 m at the time of failure), and mobilizing about 4.5 cubic kilometers reaching a maximum runout of more than 50 km. Recent research provided data on the slide deposit morphology. It was found that the upper portion of the slide, which is exposed on the seafloor, extends about 23 km seaward of the slide scar and down to water depths of 800 m. Beyond this depth the distal part of the slide (buried by glacial-time and post glacial bottom current deposits) extends over 30 km. Gondola Slide failed during the last glacial (some 25 ky BP), but strong bottom currents active in the area swept the seafloor avoiding deposition and leaving most of the blocky slide exposed. Such a large mass failure might have generated a great tsunami, which is explored in this paper by means of numerical simulations that are based on reconstruction of the geometry of the water basin at the time of failure. The numerical model, that has been developed by the University of Bologna, Italy, consists of a series of modules: the first one computes the dynamics of the sliding mass through a Lagrangian approach where the mass is partitioned into interacting blocks, the third one computes the tsunami propagation on an unstructured Eulerian grid through the shallow-water approximation of the Navier-Stokes equations, while the second one is an interpolation interface module passing data from the slide grid to the tsunami grid. This model is an enhancement of the codes that were used to study tsunami generation by the Holocene flank collapses of Stromboli and of the mount Epomeo, Ischia in the southern Tyrrhenian sea. This paper aims also at triggering a debate on the present-day tsunamigenic potential of mass failures in southern Adriatic and on the related risk.
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