GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 - POSTER GNGTS 2023 Multiscale approach to recognize seismogenic faults in offshore areas: the case of Squillace Basin (Offshore Calabria, Italy) M. Corradino *1,2 , D. Morelli 3 , S. Ceramicola 4 , L. Scarfì 5 , G. Barberi 5 , C. Monaco 1 , F. Pepe 2 1 Department of Biological, Geological and Environmental Sciences, University of Catania, Catania, Italy 2 Department of Earth and Marine Sciences, University of Palermo, Palermo, Italy 3 Department for the Earth, Environment and Life Sciences, University of Genoa, Genoa, Italy 4 OGS - Istituto Nazionale di Oceanografia e di Geofisica Applicata, Trieste, Italy 5 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, Catania, Italy Active faults are usually inferred by detecting seafloor scarps and identifying the offset of the Upper Quaternary deposits in offshore areas. Although the active faults deform a significant seafloor region, they could be secondary features formed in response to local stresses, and not associated with large earthquakes. We have reconstructed the tectono-stratigraphic architecture of the Squillace Basin (Ionian offshore of the Calabria region) from the Late Miocene to Recent, and distinguished between shallow, non-seismogenic, active faults, and deep blind faults, capable of producing large earthquakes. We have used a multiscale approach based on the interpretation of seismic reflection profiles with different penetration/resolution, calibrated with well-log data and integrated with bathymetric data, and the distribution of instrumental earthquakes. Our results highlight the occurrence of three main tectonic phases. The first extensional/transtensional phase occurred during the Late Miocene. This led to the formation of roughly W-E oriented horst and half-graben structures and a WNW-ESE transtensional fault located in the central sector of the basin (Figs. 1a-b and 2a). During the Pliocene, extensional/transtensional tectonics continued to be dominant. From the Early Pleistocene (Calabrian), the extensional tectonics was interrupted by a left-lateral transpressional phase. This last event caused the positive inversion of some deep (> 3 km) extensional faults inherited from the previous event (e.g. CDPs 600-700, 1000-1100 Fig. 1a; around CDP 200 and 700, Fig. 1b) and the formation of NW-SE to WNW-ESE transpressional/thrust faults (e.g. around CDP 2500, Fig. 1c; Fig. 2b). The anticlines, associated with these deep faults, deform the seafloor of the northern and western basin, forming NW-SE to WNW-ESE oriented ridges (Fig. 2b). The transpressional structures can be considered the offshore prolongation of the transpressional faults formed in the