Zgur, Fabrizo

The response of continental forelands to subduction and collision is a widely investigated topic in geodynamics. The deformation occurring within a foreland shared by two opposite‐verging chains, however, is uncommon and poorly understood. The Apulia Swell in the southern end of the Adria microplate (Africa‐Europe plate boundary, central Mediterranean Sea) represents one of these cases, as it is the common foreland of the SW verging Albanides‐Hellenides and the NE verging Southern Apennines merging into the SSE verging Calabrian Arc. We investigated the internal deformation of the Apulia Swell using multiscale geophysical data: multichannel seismic profiles recording up to 12‐s two‐way time (TWT) for a consistent image of the upper crust; high‐resolution multichannel seismic profiles, high‐resolution multibeam bathymetry, and CHIRP profiles acquired by R/V OGS Explora to constrain the Quaternary geological record. The results of our analyses characterize the geometry of the South Apulia Fault System (SAFS), a 100‐km‐long and 12‐km‐wide structure attesting an extensional (and possibly transtensional) response of the foreland to the two contractional fronts. The SAFS consists of two NW‐SE right‐stepping master faults and several secondary structures. The SAFS activity spans from the Early Pleistocene through the Holocene, as testified by the bathymetric and high‐resolution seismic data, with long‐term slip rates in the range of 0.2–0.4 mm/yr. Considering the position within an area with few or none other active faults in the surroundings, the dimension, and the activity rates, the SAFS can be a candidate causative fault of the 20 February 1743, M 6.7, earthquake.

High-resolution seismic reflection, magnetic and gravity data, acquired offshore of Etna volcano, provide a new insight to understanding the relationship between tectonics and spatial-temporal evolution of volcanism. The Timpe Plateau, a structural high pertaining to the Hyblean foreland domain, located offshore of southeastern Mt. Etna, is speckled by volcanics and strongly affected by strike-slip tectonics. Transpressive deformation produced a push-up and a remarkable shortening along WNW-ESE to NW-SE trending lineaments. Fault segments, bounding basinal areas, show evidence of positive tectonic inversion, suggesting a former transtensive phase. Transtensive tectonics favoured the emplacement of deep magmatic intrusive bodies and Plio-Quaternary scattered volcanics through releasing zones. The continuing of wrench tectonics along different shear zones led to the migration of transtensive regions in the Etna area and the positive inversion of the former ones, where new magma ascent was hampered. This process caused the shifting of volcanism firstly along the main WNW-ESE trending "Southern Etna Shear Zone", then towards the Valle del Bove and finally up to the present-day stratovolcano.

The response of continental forelands to subduction and oblique collision is a widely investigated topic in geodynamics. The deformation occurring within a foreland shared by two opposite-verging chains, however, is not very common and poorly understood. The Apulia block, at the southern end of the Adria microplate, Central Mediterranean, represents one of these latter cases, being the common foreland of the Dinarides and Apennines orogens. In its southern part, the Apulian foreland has preserved the Mesozoic paleomargin at the transition with the old oceanic Ionian crust that conversely underwent subduction under the Calabrian and Hellenic arcs. For these reasons, Apulia represents an interesting and rare case of study where double orogens and subduction have interacted with the foreland block. As described by various authors, the almost symmetrical bending of the Apulia foreland due the opposite load of the adjacent chains, produced a system of NW-SE trending normal faults. The precise age and the role of these faults have not been yet determined due to the lack of available information. In this contribution we investigated the internal deformation of the Apulia foreland using geophysical data at various resolutions and scales over a wide area. We used multichannel seismic profiles, part of which are provided in the collaborative framework between Spectrum Geo and INGV, recorded up to 12 s and provide a consistent imaging of the upper crustal setting of the Apulia foreland. High-resolution multichannel seismic profiles, multibeam high-resolution bathymetry and CHIRP profiles recently acquired by R/V OGS Explora provide constraints on the recent activity of the major fault systems identified. The analysis of this multiscale dataset highlights the presence and the role of a major NW-SE oriented active fault system which obliquely cuts the Apulia foreland. The presence of this fault system has already been hypothesized based on sparse seismic profiles, but its lateral continuity has never been documented. From the seismic viewpoint, this structure lies in a relatively silent area. Nonetheless, it hosts the 1743 Southern Apulia Mw 6.8 earthquake which widely damaged the Salento (S-Italy) and Ionian Islands (Greece) regions and whose source is still a matter of debate. This new geophysical dataset allowed us to reconstruct the 3D geometry of this fault system, whose architecture suggests a transtensive kinematics, and to analyse the syn-tectonic basins associated with the major faults which recorded the Late Quaternary to Holocene deformation. This work is being developed in the frame of the project “FASTMIT”, funded by the Italian Ministry of University and Research.

The TOMO-ETNA experiment was planned in order to obtain a detailed geological and structural model of the continental and oceanic crust beneath Mt. Etna volcano and northeastern Sicily up to the Aeolian Islands (southern Italy), by integrating data from active and passive refraction and reflection seismic methodologies, magnetic and gravity surveys. This paper focuses on the marine activities performed within the experiment, which have been carried out in the Ionian and Tyrrhenian Seas, during three multidisciplinary oceanographic cruises, involving three research vessels (“Sarmiento de Gamboa”, “Galatea” and “Aegaeo”) belonging to different countries and institutions. During the offshore surveys about 9700 air-gun shots were produced to achieve a high-resolution seismic tomography through the wide-angle seismic refraction method, covering a total of nearly 2650 km of shooting tracks. To register ground motion, 27 ocean bottom seismometers were deployed, extending the inland seismic permanent network of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and a temporary network installed for the experiment. A total of 1410 km of multi-channel seismic reflection profiles were acquired to image the subsurface of the area and to achieve a 2D velocity model for each profile. Multibeam sonar and sub bottom profiler data were also collected. Moreover, a total of 2020 km of magnetic and 680 km of gravity track lines were acquired to compile magnetic and gravity anomaly maps offshore Mt. Etna volcano. Here, high-resolution images of the seafloor, as well as sediment and rock samples, were also collected using a remotely operated vehicle.

The TOMO-ETNA experiment was performed in the framework of the FP7 “MED-SUV” (MEDiterranean SUpersite Volcanoes) in order to gain a detailed geological and structural model of the continental and oceanic crust concerning Etna and Aeolian Islands volcanoes (Sicily, Italy), by means of active and passive seismic exploration methodologies. Among all data collected, some 1410 km of marine multi-channel seismic (MCS) reflection profiles were acquired in the Ionian and Tyrrhenian Seas during two of the three oceanographic cruises of the TOMO-ETNA experiment, in July and November 2014, with the aim of shading light to deep, intermediate and shallow stratigraphy and crustal structure of the two above mentioned areas. The MCS sections, targeted to deep exploration, were acquired during the oceanographic cruise on board of the R/V “Sarmiento de Gamboa”, using an active seismic source of 16 air-guns, for a total volume of 4340 cu. in., and a 3000 m long, 240-channels digital streamer as receiving system. High-resolution seismic profiles were instead collected through the R/V “Aegaeo”, using two smaller air-guns (overall 270 cu. in. volume) and a 96 channels, 300 m long digital streamer. This paper provides a detailed description of the acquisition parameters and main processing steps adopted for the MCS data. Some processed lines are shown and preliminarily interpreted, to highlight the overall good quality and the high potential of the MCS sections collected during the TOMO-ETNA experiment.

The presence of a seamount-like structure, located a few nautical miles offshore the Capo Vaticano Promontory (western Calabria, S Italy), was revealed by combined geophysical and geochemical investigation. The edifice covers ~55 km2, with a top located at a depth of about 70 m below sea level, and consists mainly of a NW-trending structure orthogonally interrupted by minor ridges, the largest of which is affected by extensional faults. The top of the edifice hosts active vents, injected fluids that have been investigated for dissolved volatiles. Gas analyses revealed high CO2 and CH4 contents, several orders of magnitude above the atmospheric-type values expected for shallow, coastal marine waters, and a noteworthy enrichment in mantle-derived 3He, which is an unambiguous indicator of the mantle origin of the fluids. Our results, combined with available data from the literature, suggest that the edifice is a tectonically controlled volcanic system, which presence near the Calabria region changes the role played by faults in the frame of the subduction process.

Recognizing the seismogenic source of major historical earthquakes, particularly when these have occurred offshore, is a long-standing issue across the Mediterranean Sea and elsewhere. The destructive earthquake (M ~7) that struck western Calabria (southern Italy) on the night of 8 September 1905 is one such case. having various authors proposed a seismogenic source, with apparently diverse hypotheses and without achieving a unique solution. To gain novel insight into the crustal volume where the 1905 earthquake took place and to seek a more robust solution for the seismogenic source associated with this destructive event, we carried out a well-targeted multidisciplinary survey within the Gulf of S. Eufemia (SE Tyrrhenian Sea), collecting geophysical data, oceanographic measurements, and biological, chemical and sedimentary samples. We identified three main tectonic features affecting the sedimentary basin in the Gulf of S. Eufemia: 1) a NE-SW striking, ca. 13-km-long, normal fault, here named S. Eufemia Fault; 2) a WNW-striking polyphased fault system; and 3) a likely E-W trending lineament. Among these, the normal fault shows evidence of activity witnessed by the deformed recent sediments and by its seabed rupture along which, locally, fluid leakage occurs. Features in agreement with the anomalous distribution of prokaryotic abundance and biopolymeric C content, resulted from the shallow sediments analyses. The numerous seismogenic sources proposed in the literature during the past 15 years make up a composite framework of this sector of western Calabria, that we tested against a) the geological evidence from the newly acquired dataset, and b) the regional seismotectonic models. Such assessment allows us to propose the NE-SW striking normal fault as the most probable candidate for the seismogenic source of the 1905 earthquake. Re-appraising a major historical earthquake as the 1905 one enhances the seismotectonic picture of western Calabria. Further understanding of the region and better constraining the location of the seismogenic source may be attained through integrated interpretation of our data together with a) on-land field evidence, and b) seismological modeling.

During the summer of 2010 we carried out a survey to acquire a multidisciplinary dataset within the Gulf of Sant'Eufemia (SE Tyrrhenian sea, Italy), with the aim of studying the active tectonics affecting the region, including that potentially responsible for key, elusive earthquakes such as the to-date unexplained 8 September 1905 (Mw 7 - 7.5) earthquake. The data here analysed highlight the presence of several tectonic and morphologic features characterizing the investigated area. We have recognized the Angitola Channel, a deep and wide canyon showing a straight trend in its coastward segment, and a meandering trend in the seaward segment. Based on morpho-structural elements, we maintain that the Angitola Channel could be tectonically controlled. Moreover, several gravitational instabilities as slumps and collapses affect the flanks of the morpho-structural high, detected offshore Capo Vaticano. Very high resolution seismic data have unveiled the presence of numerous fluid escape features and several mud volcanoes straddling the sector from the coastline to seaward.