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Crystalline rocks can produce dangerous radiation levels on the basis of their content in radioisotopes. Here, we report radiological data from 10 metamorphic and igneous rock samples collected from the crystalline basement of the Peloritani Mountains (southern Italy). In order to evaluate the radiological properties of these rocks, the gamma radiation and the radon emanation have been measured. Moreover, since some of these rocks are employed as building materials, we assess the potential hazard for population connected to their use. Gamma spectroscopy was used to measure the 226Ra, 232Th and 40K activity concentration, whereas the radon emanation was investigated by using a RAD 7 detector. The results show 226Ra, 232Th and 40K activity concentration values ranging from (17 ± 4) to (56 ± 8) Bq kg−1, (14 ± 3) to (77 ± 14) Bq kg−1 and (167 ± 84) to (1760 ± 242) Bq kg−1, respectively. Values of the annual effective dose equivalent outdoor range from 0.035 to 0.152 mSv y−1, whereas the gamma index is in the range of 0.22–0.98. The 222Rn emanation coefficient and the 222Rn surface exhalation rate vary from (0.63 ± 0.3) to (8.27 ± 1.6)% and from (0.12 ± 0.03) to (2.75 ± 0.17) Bq m−2 h−1, respectively. The indoor radon derived from the building use of these rocks induces an approximate contribution to the annual effective dose ranging from 8 to 176 μSv y−1. All the obtained results suggest that the crystalline rocks from the Peloritani Mountains are not harmful for the residential population, even though they induce annual effective doses due to terrestrial gamma radiation above the worldwide average values. Moreover, their use as building materials does not produce significant health hazards connected to the indoor radon exposure.

The south-western edge of the Calabrian Arc in southern Italy has been investigated throughout a joint analysis of field, marine and geophysical data which provided constraints on the fault pattern and on the seismotectonic potential. The study was focused on a poorly known sector of a larger belt of seismically active faults slicing across the NE corner of Sicily, the so-called Tindari Fault System. Our data pointed out that the investigated area, including the mainland and the Ionian offshore, is deformed by oblique faulting with a general NW-SE tectonic trend. Earthquake distribution and seismic profiles pointed out active deformation in the offshore while the mainland is characterized by the occurrence of a NW-SE oriented, >20 km-long, structural belt. However, scarce seismicity has been recorded in the last 30 years alongside this tectonic structure, accounting for a possible silent segment of the larger fault system. Tomographic images revealed that the Moho discontinuity is deformed by a NE-dipping lithospheric tectonic structure which has been here retained the main mode of deformation and responsible for coseismic displacement in the area. As a whole, field and geophysical data agree with a general NW-SE trend segmented pattern of recent/active faults that have the potentiality of generating magnitude 6.5–7 earthquakes.

The Calabrian Arc subduction-rollback system along the convergent Africa/Eurasia plate boundary is among the most active geological structures in the Mediterranean Sea. However, its seismogenic behaviour is largely unknown, mostly due to the lack of seismological observations. We studied low-to-moderate magnitude earthquakes recorded by the seismic network onshore, integrated by data from a seafloor observatory (NEMO-SN1), to compute a lithospheric velocity model for the western Ionian Sea, and relocate seismic events along major tectonic structures. Spatial changes in the depth distribution of earthquakes highlight a major lithospheric boundary constituted by the Ionian Fault, which separates two sectors where thickness of the seismogenic layer varies over 40 km. This regional tectonic boundary represents the eastern limit of a domain characterized by thinner lithosphere, arc-orthogonal extension, and transtensional tectonic deformation. Occurrence of a few thrust-type earthquakes in the accretionary wedge may suggest a locked subduction interface in a complex tectonic setting, which involves the interplay between arc-orthogonal extension and plate convergence. We finally note that distribution of earthquakes and associated extensional deformation in the Messina Straits region could be explained by right-lateral displacement along the Ionian Fault. This observation could shed new light on proposed mechanisms for the 1908 Messina earthquake.

Using seismic reflection profiles and bathymetric data, we analyzed the stratigraphy and tectonics of the Paola Basin, providing information on the dynamic of the forearc of the Tyrrhenian-Ionian subduction system. The Paola Basin is a NNW-SSE trending syncline, bounded by the Coastal Chain to the east and the Paola Anticline to the west. It hosts up to 5.2 km thick Plio-Quaternary deposits, most of them supplied from Apenninic/Sila entry points and transported by longshore currents. The total subsidence reaches a value of ∼5 km. The sedimentary load varies from 60% to 75% of the total subsidence. The Pliocene to Lower Pleistocene sedimentary infill of the syncline displays a strata growth geometry consistent with a continuous rotation of the eastern limb of the Paola Anticline. Crustal folding can explain both the tectonic subsidence of the Paola Basin and the uplift of the Paola Anticline. To the east of the basin, Late Pliocene to Early Pleistocene growth of the central sector of the Coastal Chain led to the definition of the Paola and Crati basins, previously connected in a larger proto basin. The trench-parallel component of the plate movement was accommodated by a strike-slip zone, with associated releasing and restraining bends coinciding with the Paola Anticline. The bathymetric expression of the strike-slip zone consists of structural highs and depressions that overall form the Paola Ridge. Since the Middle Pleistocene, the growth of the Paola Anticline and Paola Basin came to an end and extensional tectonics controlled the evolution of the forearc region.

11 pages, 7 figures, supplementary material https://doi.org/10.1016/j.epsl.2020.116480, The formation of Cenozoic mountain belts in the Mediterranean realm was preceded by tens of millions of years of subduction, forming volcanic arcs, and frontal contractional systems. In addition, subduction usually involves slab rollback and formation of oceanic backarcs. Although such structure must have influenced the orogeny of Mediterranean mountain belts, no active analog has been mapped with modern crustal-scale seismic methods. Here, we study the entire Calabrian subduction system to map the structure resulting from Tethys lithosphere subduction and slab rollback, in a process that must be akin to that operating during a phase of the formation of the Mediterranean orogenic belts. We present a crustal-scale cross section of the entire Calabrian subduction system obtained from on- and off-shore wide-angle seismic data. The 2D P-wave velocity section shows spatially abrupt (, The CHIANTI survey was part of the HADES project funded by the Spanish MINECO (Ref # CTM2011-30400-C01 and CTM2011-30400-C02). [...] M. Prada is funded by the Beatriu de Pinós postdoctoral programme of the Government of Catalonia's Secretariat for Universities and Research of the Ministry of Economy and Knowledge (Ref # 2017BP00170), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

The Pliocene-Quaternary evolution of the western margin of the Calabrian Arc has been investigated by analysing the configuration and distribution of local sedimentary basins and their relationship with shallow and deep tectonic structures. Research focussed on the evolution of the more recent offshore sedimentary basins located to the east of Sicily, along the Alfeo Fault System, using multichannel seismic lines, high-resolution bathymetry and newly acquired single-channel seismic profiles. The chosen study area encompasses a crustal sector where external thrusts of the Calabrian Arc branch into the Malta Escarpment, and this zone has been interpreted as a Subduction Transform Edge Propagator (STEP) Fault. The Western Ionian Sea is bounded by regional faults that controlled the deposition of the Pliocene-Quaternary sequences and define the present-day bathymetry. In this work we identified four main seismic sequences and three main unconformities in the basins, to better understand the geometry and the depositional setting of the basins. In addition, lateral correlation and 3D reconstruction of the sedimentary basins allows us to establish the direct relationship between the Alfeo Fault System activity and the geometry, the thickness, the evolution and filling phases of the sedimentary basins in this area. Results presented show how the Alfeo Fault drove the development of separate basin depocenters in the early stages of tectonic activity, resulting in a single elongated basin in the latest phases. The inferred fault kinematics, the analysis of displacements along strike and sediment thickening suggest a link with the slab geometry, as occurs in other subduction systems that develop subduction related faults. The results and the method applied in this study can also be applied for the interpretation of similar systems with similar geological settings in other areas of the world.

The Calabria Arc presents the highest probability of occurrence of major earthquakes in the Italian peninsula. Several destructive historical earthquakes (i.e. 1638, 1659, 1783, 1905 and 1908) affected, in particular, the Catanzaro Trough and its neighbouring areas. These events have been tentatively related to the activity of NE-SW trending normal faults. Some of these earthquakes have been followed by tsunamis, which caused further damages along the Tyrrhenian coast. In this paper, we reconstruct the Quaternary evolution of the Catanzaro Trough by combining field geo-structural and marine geophysical data. The results have been compared with existing database of earthquake focal mechanisms, updated with 8 new focal solutions performed in the present work. Analysis of faults offsetting the Lower-Middle Pleistocene deposits shows that the Catanzaro Trough experienced transcurrent and extensional phases of deformation. In particular, conjugate systems with NW-SE right-lateral and NE-SW left lateral faults were observed to displace the Lower Pleistocene deposits. Whereas NE-SW and N-S oriented normal faults have been identified as the main fault systems acting during late Pleistocene-Holocene phase. The interpretation of on-land structural datasets has been supported by geophysical data (multichannel and Chirp profiles) acquired in the offshore and onshore of the study area. Multidisciplinary approach has allowed to define NE-SW elongated sedimentary basins, as the Lamezia Basin, bordered on the one hand by Sant'Eufemia Fault that may extend up to 30 km-length, on the other hand by two overstepping faults, Vibo Valentia and San Pietro Lametino Faults. These findings carry some relevant implications in terms of seismic hazard, as they suggest that the longer fault segment, the greater its energetic seismic event. Finally, these data fit perfectly with the observed late Pleistocene-Holocene WNW-ESE extensional stress regime derived from existing and new database of earthquake focal mechanisms. This is in agreement with the orientation of the most seismically active grabens of the Calabrian Arc (the Crati, the Mesima and the Gioia Tauro Basins). Amongst these structural lineaments, the NE-SW and N-S trending normal faults play surely a relevant role as part of recent seismotectonics processes controlling the Late Quaternary geodynamics of the central Calabrian Arc, representing the source of the main destructive earthquakes occurred in the region.

The Lower Pliocene succession of the Crotone Basin (Calabrian Arc, Southern Italy) is mainly comprised of blue-grey marly clay with good magnetic properties. Here the bio-magnetostratigraphic data indicate a mean sedimentation rate of about 12–15 cm/kyr. Around 3.7–3.6 Ma a major change in the sedimentation regime occurred: the blue-grey hemipelagic marls grade rapidly into silty marls with a significant increase in the terrigenous fraction and with abundant siliceous remains throughout the whole interval. Magnetic properties of these sediments are very poor, but an integrated calcareous plankton biostratigraphy (foraminifera and nannofossils) infers a high average sedimentation rate (about 50–60 cm/kyr). The abrupt onset of this sedimentation regime in the Crotone Basin is contemporaneous with a major unconformity already recognized in the northern sector of the basin, part of a major reorganization phase in the whole Apenninic–Maghrebid Chain known as “Globorotalia puncticulata event”. Reports of coeval siliceous sediments in other marginal basins of the Apennines (Southern Calabria, Southern and Northern Apennines) suggest that this “siliceous event” might have been regionally extensive, having important palaeoceanographical implications. We infer that the “siliceous event” is characterized by a combined tectonic- and climate-induced change in palaeoceanographic conditions. The tectonic triggering factors may have been linked to two synchronous events in the Tyrrhenian–Apennine system: 1) the shortening event also known as “G. puncticulata event”, and 2) the coeval opening of the Vavilov Basin in the Tyrrhenian Sea which yielded profound influences in terms of physiography and characteristics of the Crotone Basin. The consequent uplift of the Southern Apennines would have increased sediment supply and availability of silica, resulting in eutrophication and enhanced silica preservation. Strong winter mixing and possibly upwelling conditions could have increased primary productivity during heavy isotope stages Gi4, Gi2 and MG8, at the onset of the “siliceous event”. This important event, lasting from ca. 3.6 Ma to ca. 3.2 Ma, would have recorded a peculiar transitional period before further climatic deterioration and more drastic palaeoceanographic changes occurred around 3.1 Ma, leading to cyclic sapropel deposition in the whole of the Mediterranean sea.

A Middle Miocene-Middle Pleistocene regional NW-SE left-lateral strike-slip fault system profoundly conditioned the evolution of central Calabria, during the late tectonic phases which involved the Apulian block and the Calabrian Arc. This system dissected an Oligocene-Early Miocene orogenic belt, made of Alpine nappes overthrusted the Apennine Chain. In the present study, three major faults, arranged in a right-hand en echelon pattern, have been identified within the mentioned strike-slip system: the Falconara-Carpanzano Fault, the Amantea-Gimigliano Fault, and the Lamezia-Catanzaro Fault. A wide active transtensional area (N-S-trending Crati Graben), developed since Late Pliocene, is located at the SE termination of the Falconara-Carpanzano Fault. In the sectors of overlapping of the faults, the transpressional regime induced tectonic extrusions of the deep-seated units of the Chain, producing push-ups within the overlying complexes. In particular, push-ups are either made of Mesozoic carbonate rocks at Mt. Cocuzzo–Mt. Guono and Mt. S. Lucerna, or of ophiolite rocks at Mt. Reventino and Gimigliano. In these sectors, the primary geometric relationships among the units of the orogenic belt were locally altered. The en echelon arrangement of the above-mentioned NW-SE major strike-slip faults indicates the existence of a left-lateral crustal shear zone, striking on average N160. The age of the regional NW-SE left-lateral strike-slip system deserves thorough investigation. Besides evidence from historical and instrumental earthquakes, and from paleoseismological investigations, the kinematic data suggests that the “cause” of the transtensional sector (Crati Graben) could be found in the regional Falconara-Carpanzano Fault.

In 1998-1999 a seismic sequence occurred in the Southern Apennines, after the moderate size (mb=5.0) 9th September 1998 Pollino earthquake. It lasted about 14 months and was clearly localized to the sole north-west area of the main shock epicenter. Its peculiarity consisted in sudden changes of activity from a series of normal faults with Apenninic (NW-SE) trend and transfer, presumably strike slip, faults with Antiapenninic (NE-SW) and E-W trend. The complexity of the behavior and the different orientations of the activated systems suggest that the area acts as a hinge between the NW-SE trending Southern Apennines and the locally N-S trending Calabrian Arc.

The Straits of Messina and its surroundings are considered as one of the most tectonically active area of the Mediterranean. but in spite of their hazard potential. modern geophysical data aimed at investigating their hidden structures are lacking In order to bridge this gap, we carried out a marine multichannel seismic survey primarily aimed at: i) studying the regional fault pattern in the area of the Messina 1908 earthquake, and ii) checking the existence of a potentially seismogenic fault, the Taormina Fault, Which many authors locate offshore, along the coast between Taormina and Messina. Our seismic :)profiles show a great structural complexity within the Messina Straits. with the best imaged faults occurring on the Calabrian side In particular, a more than 30 km long NW-trending fault located at the SW tip of Calabria is cutting the sea floor Moreover, our data did not image any extensional fault plane attributable to the Taormina Fault: rather, the whole slope has been tilted east-ward The geodynamic Implication is that extension in south-eastern Sicily, on the Ionian side of the Hyblean Plateau, and extension in southern Calabria and Messina Straits belong to two different tectonic systems and cannot be mechanically linked.

Southern Italy is dominated by extensional tectonics that in the Calabrian arc and Eastern Sicily produced the development of the Siculo–Calabrian Rift Zone (SCRZ). This zone is represented by a ≈ 370 km-long fault belt consisting of 10 to 50 km long distinct fault segments which extend both offshore and on land being also responsible of the crustal seismicity of this region. The geological and morphological observations indicate that the active normal faults of the SCRZ are characterized by throw-rates ranging from 0.7 to 3.1 mm/a. They accommodate an almost uniform horizontal extension-rate of about 3.0 mm/a along a WNW–ESE regional extension direction. Based on our field observations and following empirical relationships between magnitude and surface rupture length connections between large crustal earthquakes and distinct fault segments of the SCRZ have been also tentatively tested. Our data indicate moreover that the magnitudes (M) of the historical and instrumental earthquakes are consistent with the estimated values and that the geometry and kinematics of the fault segments and the related different crustal features of the SCRZ control the different seismic behaviours of adjacent portions of the active rift zone.

Comparing two sections through the Apennine subduction zone (Italy), the slab is far deeper (>500 km) beneath the Calabrian arc than beneath the northern-central Apennines (