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Orographic reliefs are continuously created and modified in active continental tectonic settings, influencing the drainage pattern and interacting with it. It is not uncommon that stream capture occurs in these settings, causing major rearrangement of river courses. This process often produces a geomorphological feature known as wind gap, i.e. a gap through which a stream once flowed but that is now abandoned and dry as a result of the capture. Analizing a high resolution 3D seismic data set, kindly made available by ENI S.p.A., we discovered a similar feature in the Ionian offshore of the Crotone peninsula, northern Calabria. This underwater region is characterized by intense tectonic activity that is partly controlled by the occurrence of a mobile substrate, possibly overpressured shales. The relevant uplift affecting the nearby Calabria onshore can also contribute to promote gravitational instability. In this setting the "wind gap" is represented by a stretch of a downslope weakly incised channel that has soon been abandoned as a result of the growth of a tectonic structure. The course of the new submarine channel runs sub-parallel to the coast for a long strecth, before taking a downslope trajectory. The present-day submarine channel is deeply incised, showing at least two main phases: a deep valley incision containing an axial valley with a much lower relief, which likely represents the current route of turbidite flows. The main channel valley results from the major erosional episode that affected the continental slope offshore northern Calabria. The limited incision in the abandoned channel strecth suggests that drainage rearrangement occurred in the very early stage of channel incision. Therefore, the estimated age of the tectonic deformation that is responbile for originating the "wind gap" can offer a useful hint on the timing of onset of erosion in this area.

Ground motion prediction is one of the main goals in seismic hazard assessment. Empirical ground motion prediction equations may fail to reproduce the complexity of ground shaking in complex 3D media and therefore the use of full waveform modelling is increasingly adopted to model ground shaking. The knowledge of the 3D crustal structure in terms of geometries of the main discontinuities and velocities is fundamental to model wave propagation. However, we often lack detailed geological and geophysical information to build reliable models.We exploit here a large set composed of high-resolution 2D and 3D seismic data and of about 40 wells with stratigraphic and velocity information, both onshore and offshore, to constrain a 3D crustal velocity model in a sector of the Calabrian accretionary prism (southern Italy). We interpret the main reflection discontinuities and constrain their depth at all available wells in the study area and we use well’s check-shots and velocity data to estimate interval-velocities of the main stratigraphic units. We then combine all depth and velocity information into a regional 3D crustal velocity model of the first 8-10 km. This is subsequently extended to a depth of ~50 km using available regional crustal models to obtain the final model used for ground motion simulation.We implement our crustal model in the spectral-element code SPECFEM3D_Cartesian to simulate wave propagation in the 3D velocity model honoring surface topography. This allows reconstructing the low-frequency part of the waveforms (up to ~1 Hz), which is then combined with high-frequency seismograms obtained with a stochastic method following the hybrid broadband simulation approach by Graves and Pitarka (2010).We evaluate the goodness of our model by simulating real earthquakes and comparing simulated and recorded waveforms at the available seismic stations in the area. We compare the results from our 3D model with the ones obtained using a local tomography model and the European crust model EPcrust. The maps of ground motion obtained from the simulated broadband waveforms are then compared with empirical ShakeMaps. These results will also be useful for earthquake scenario calculations, by simulating potential seismic sources identified from structural analysis of geological and seismic data.

The Calabrian accretionary prism is the result of a complex interaction between subduction-related tectonics and sedimentation, active since the Eocene. The limited seismicity recorded in recent years in the area appears mostly associated to the subduction interface and could reflect either a weak subduction coupling or a slow subduction rate. Nevertheless, recent intense deformation and uplift of the seafloor has been observed within the accretionary prism.The analysis of multichannel 2D and high-quality 3D seismic data, morphobathymetric data and instrumental seismicity, allows defining and characterizing both the deeper and shallower tectonic deformation affecting the northeastern sector of the Calabrian accretionary prism. Besides the uppermost thrust fault of the Calabrian accretionary prism, that outlines the Crotone promontory, the shallow tectonic pattern of the prism is characterized by a belt of broad flat-topped anticlines, and a set of minor narrow structures, mainly NNW-SSE to N-S oriented, that present a variable relationship with the underlying main thrust faults. The uppermost sedimentary strata within the anticlines are affected by numerous small-scale extensional faults, not rooted at depth, likely due to outer-arc extension above uplifted depocenters. In places, the inversion of basin-bounding faults is also visible. More regularly spaced and cylindrical NW-SE anticlines are also observed in the Gulf of Taranto, in the outer sector of the accretionary prism, where a thrust/back-thrust tectonic style is present. The origin of the anticlines varies within the overall set and reflects the long-term tectonic evolution of the accretionary prism, with the oblique docking of the Calabrian accretionary prism onto the Apulian Escarpment as a key feature.

At 3:54 night time on November the 26th the city of Durres in Albania was hit by an earthquake of Mw 6.2, followed in the next 4 hours by three additional earthquakes with Mb > 5.0. These earthquakes, part of a sequence that continued with much reduced intensity until mid December, caused severe damages in Durres and the adjacent region, counting a final human toll of about 50 casualties and over 2000 injuried. The historical catalogues show that Albania has been affected by over 10 relatively strong earthquakes (Mw> = 6.0) in the last 200 years (Kiratzi and Dimakis 2013), testifying to an important seismic history.The focal mechanisms of the Durres earthquakes show compressive fault planes placed at ca. 10 km depth. These earthquakes are part of a belt of compressional earthquakes that borders to the east the southern Adriatic, including the strong Montenegro earthquake (Mw 7.1) of April 1979, indicating that shortening is currently ongoing at the front of the southern Dinarides and Hellenides.The geological structure of Albania, at the junction between the Dinarides and the Hellenides, shows structural complexities that have their roots in the Mesozoic paleogeography of the region (Argnani, 2013). The front of the Albanian fold-and-thrust belt extends to the sea, where it has been studied thanks to some seismic acquisition campaigns aimed at investigating the geology of the Adriatic Sea (Argnani 2013). This sector of the thrust front is characterized by the presence of important back thrusts, which are correlated to the spatial distribution of the Mesozoic domains of carbonate platforms and pelagic basins. In the sector facing the southern Adriatic basin the presence of a large thickness of Oligocene-Quaternary clastic sediments filling the foredeep promotes the development of triangle zones and backtrusts. The basal thrust of the triangle zone system affects Mesozoic carbonates at an estimated depth of 10-15 km (Fantoni and Franciosi, 2010) and appears to be the source of the Durres earthquakes. A similar structural setting can be envisaged for the Montenegro earthquake of 1979, as the offshore structures show a continuity, although a substantial change in strike occurs across the trend of the Shkoder-Peja line. A large lateral displacement of the internal units occurs along the Shkoder-Peja transversal line, which marks the junction between the Hellenides and the Dinarides. The shallow water limestones of the more external Kruja domain, however, are not laterally offset. Palaeomagnetic results indicate that the Miocene-Pliocene clock-wise rotation of the western arm of the Aegean opening was accomplished just south of the Shkoder-Peja line; these rotations impose an overall change in strike of the outer thrusts, although the frontal structures are specifically affected by the nature of the Mesozoic domains entering the thrust system.ReferencesArgnani A. (2013) -. Ital. J. Geosci., 132, 175-185.Fantoni R., Franciosi R. (2010) - Rend. Fis. Acc. Lincei 21, S197–S209.Kiratzi A., Dimakis E. (2013) - Ital. J. Geosci., 132, 186-193.