<p>The Western Calabrian margin (Italy) is the most active segment of the Apennine back-arc system, formed in response to the slow Africa &#8211; Eurasia convergence. The offshore area represents the transitional region between the arc and the back-arc: it is affected by several fault systems, most of them able to trigger highly destructive earthquakes. Indeed, the Calabria and its western offshore are characterized by the highest seismic moment release of the entire Apennines, also evidenced by historical seismicity catalogue, the most accurate over the world. During last decades, scientific community invested huge resources in assessment of seismic and tsunami hazards. Furthermore, during last years several local-scale works allowed of improving knowledge of the faults geometry, magmatism, seismogenic and tsunamigenic potential along the western offshore region (Loreto et al., 2017; Brutto et al., 2016; De Ritis et al., 2019). Some active faults, belonging to NE-SW-trending normal fault systems accommodating the inner-arc collapse related to slab-decupling, are also responsible of the most destructive historical sequences, still to be adequately characterized. Using vintage SPARKER 30 Kj acquired in the seventies and recent multichannel seismic profiles together with middle resolution morpho-bathymetric data we produced a new tectonic map of the Calabria back-arc system. Further, we characterized some before-unknown faults and linked them with shallow structures, as ridges and slumps / slides. This area seemingly less populated of faults compared to the peri-Tyrrhenian margin, where several faults belong to different systems, i.e. (i) the rifting system active that allowed the opening of the Tyrrhenian Basin and (ii) the slab-decupling related normal faults system currently active. The comparison with historical and instrumental seismicity allowed us to highlight possible seismic gaps that, if considered, could strongly improve the map of seismogenic potential of the Tyrrhenian back-arc system.</p><p>&#160;</p><p>Bibliography</p><p>Brutto, F. et al. (2016). The Neogene-Quaternary geodynamic evolution of the central Calabrian Arc: A case study from the western Catanzaro Trough basin. Journal of Geodynamics, 102, 95-114.</p><p>Loreto, M. F. (2017). Reconstructed seismic and tsunami scenarios of the 1905 Calabria earthquake (SE Tyrrhenian sea) as a tool for geohazard assessment. Engineering geology, 224, 1-14.</p><p>Tripodi, V. et al. (2018). Neogene-Quaternary evolution of the forearc and backarc regions between the Serre and Aspromonte Massifs, Calabria (southern Italy). Marine and Petroleum Geology, 95, 328-343.</p>
The central Red Sea, an oceanic basin floored by Miocene evaporites reaching kilometres in thickness in places, is at an early stage of development, where seafloor spreading has geologically only recently replaced continental rifting.Surveying with a high-resolution multibeam echo-sounder around Thetis Deep, a new spreading centre, has revealed a remarkable series of structures resembling viscous gravity flows, which are here interpreted as originating from flowage of the evaporites laterally unloaded by axial rifting and other processes developing the relief of the deep.The flow margins are marked by stream-wise lineaments and some apparently rotated markers.Their fronts in the floor of the deep are rounded in plan view and profile.Their surfaces contain small closely spaced features resembling extensional faults.In one area below declining gradients, the surface contains along-slope ridges and valleys typical of compression folds (ogives).Flow-parallel lineaments and extensional faults lie, respectively, parallel and orthogonal to the direction of maximum seabed gradient.Movement is apparently heterogeneous, at least in part by varied blocking by relief of underlying basement observed protruding between flows.Flowage is currently transporting materials into the floor of the deep where it has the potential to become incorporated into the young oceanic crust by repeated eruption of axial lavas over them.In the light of these new data, we reexamine the possibility and implications of flowage in the South Atlantic marginal evaporites, in particular whether flowage contaminated early oceanic crust in such areas.
The MaGIC project (Marine Geohazard along the Italian Coasts) had the aim of mapping the geohazard in the Italian seas and resulted in the production of numerous maps covering parts of the Italian Seas. In this paper, we present the maps: 'The submerged portions of the Aeolian volcanic islands and the north-eastern Sicilian margin', located in the south-eastern Tyrrhenian Sea. Both areas are affected by active geological processes, which represent important geohazards elements. Inthe submarine parts of the Stromboli volcanoremobilization of volcaniclastic deposits occur along the Sciara del Fuoco, where small-scale instabilities may represent a source of geohazard. Hydrothermal activity occurs on Enarete and Enaretino conical seamounts. The north-eastern Sicilian margin has a narrow continental shelf. Numerous canyon heads indent the shelf and, sometimes, reach close to the coast. Canyons have often a retrogradational trend and further eventual landward shift through sliding can iendangeri coastal or offshore infrastructures. Many of the canyons connect with leveed channels with widespread sediment instability. In the Gioia Basin, some of the channels connect to form the Stromboli slope Valley. Volcanic unrest or local and regional earthquakes are proven to have caused submarine landslides and tsunamis.
The central Red Sea, an oceanic basin floored by Miocene evaporites reaching kilome ters in thickness in places, is at an early stage of development, where seafl oor spreading has geologically only recently replaced continental rifting. Surveys using a high-resolution multibeam echo sounder around Thetis Deep, a new spreading center, have revealed a remarkable series of structures resembling viscous gravity fl ows, which are here interpreted as originating from fl owage of the evaporites laterally unloaded by axial rifting and other processes developing the relief of the deep. The fl ow margins are marked by stream-wise lineaments and some apparently rotated markers . Their fronts in the fl oor of the deep are rounded in plan view and profi le. Their surfaces contain small, closely spaced features resembling extensional faults. In one area below declining gradients, the surface contains along-slope ridges and valleys typical of compression folds (ogives). Flowparallel lineaments and extensional faults lie, respectively, parallel and orthogonal to the direction of maximum seabed gradient. Movement is apparently heterogeneous, at least in part because of varied blocking by relief in underlying basement observed protruding between fl ows. Flowage is currently transporting materials into the fl oor of the deep where they have the potential to become incorporated into the young oceanic crust by repeated eruption of axial lavas over them. In the light of these new data, we reexamine the possibility and implications of fl owage in the South Atlantic marginal evaporites, in particular, whether fl owage contaminated early oceanic crust in such areas.
The Calabrian Arc is a narrow subduction-rollback system resulting from Africa/Eurasia plate convergence. We analysed the structural style of the frontal accretionary wedge through a multi-scale geophysical approach. Pre-stack depth-migrated crustal-scale seismic profiles unravelled the overall geometry of the subduction complex; high-resolution multi-channel seismic and sub-bottom CHIRP profiles, together with morpho-structural maps, integrated deep data and constrained the fine structure of the frontal accretionary wedge, as well as deformation processes along the outer deformation front.We identified four main morpho-structural domains in the western lobe of the frontal wedge: the proto-deformation area at the transition with the abyssal plain; two regions of gentle and tight folding; a hummocky morphology domain with deep depressions and intervening structural highs; a highstanding plateau at the landward limit of the salt-bearing accretionary wedge, where the detachment cuts through deeper levels down to the basement. Variation of structural style and seafloor morphology in these domains are related to a progressively more intense deformation towards the inner wedge, while abrupt changes are linked to inherited structures in the lower African plate. Our data suggest focusing of intense shallow deformation in correspondence of deeply rooted faults and basement highs of the incoming plate.Back-arc extension in the Southern Tyrrhenian Sea has recently ceased, producing a slowdown of slab rollback and plate-boundary re-organization along trans-tensional lithospheric faults segmenting the continental margin. In this complex setting, it is not clear if the accretionary wedge is still growing through frontal accretion. Our data suggest that shortening is still active at the toe of the wedge, and uplift rates along single folds are in the range of 0.25-1.5 mm/yr. An unconformity within the Plio-Quaternary sediments suggests a discontinuity in sedimentation and tectonic processes, i.e. a slowdown of shortening rate or an increase in sedimentation rate, but not a real inactivation of frontal accretion, which still contributes to the migration of the outer deformation front towards the foreland.
The Stromboli geophysical experiment, performed to acquire onshore and offshore seismic data through a combined on-land and marine network, was finalized to reconstruct the
seismic tomography of the volcano and to investigate the deep structures and the location of magma chambers. A detailed swath bathymetry around the volcano has also been acquired by the R/V Urania Multibeam. In particular, high resolution bathymetry of the ’Sciara del Fuoco’ area allows to image the present-day seafloor setting of the area involved by the submarine slide of 2002-12-30. During the experiment wide angle refraction seismics was performed all around the Stromboli volcano by a 4 GI-GUN tuned array. The data were recorded by the permanent seismic network of the INGV and 20 temporary stations and 10 OBS deployed on the SE, SW and NE submerged flanks of the volcano after detailed morpho-bathymetric analysis.
