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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. • We studied a poorly known sector of the Tindari Fault System, an active faults belt slicing across the NE Sicily. • Data highlight that the studied sector has been deformed by oblique NW-SE trending faulting. • Earthquake distribution and seismic profiling evidenced active deformation. • A seismic gap in the area has been attributed to a silent segment of the analysed fault system • Lithospheric deformation is expressed by a large transtensional fault which deforms the Moho [ABSTRACT FROM AUTHOR]

Tectonic forcing causes the relief-building of mountain chains and enforces the surficial processes in a persistent dismantling of rock volumes, continuously modelling Earth's surface. Actually, we observe transient landscapes that have temporarily recorded tectonic forcing as a codified signal. The Late Quaternary tectonic evolution of northeastern Sicily, located along the Nubia-Eurasia plate boundary at the southern termination of the Calabrian arc, has been dominated by intense Plio-Pleistocene dynamics that severely modified the Late Miocene landscape. The present work aims to investigate geomorphically northeastern Sicily, essentially focusing on the hypsometric and relief analyses of the region in order to define how the topography responds to the post-Pliocene tectonic deformation. We apply different relief morphometric indices (Hypsometric Integral, Topographic Relief and Topographic Dissection) measured for each differently sized moving window, and we use different swath topographic profiles as well. Our analysis evidences differential morphological responses between distinct morphotectonic domains of the studied area, led by the combination of earlier morphological background and Late Quaternary tectonic deformation stages of the region. In addition, in the context of a constant and uniform tectonic uplift, the results define the general space- and time-relating pathways of the landscape geomorphic metrics. This enables us to bring out the controls of the vertical scale of landscape on hypsometry, exploring their mutual relationships. Finally, we reconstruct the Late Quaternary morphotectonic evolution of the region, defining the role played by the main tectonic alignments on the present geomorphic setting. [ABSTRACT FROM AUTHOR]

Between June 2011 and September 2013, the Nebrodi Mountains region was affected by a seismic swarm consisting of > 2700 events with local magnitude 1.3 ≤ M L ≤ 4.6 and located in the 5–9 km depth interval. The seismic swarm defines a seismogenetic volume elongated along the E-W direction and encompasses the NW-SE-oriented tectonic boundary between the Calabrian arc (north-eastward) and the Sicilide units (south-westward). By exploring the recent tectonic deformation and the seismic behavior of the region, this study aims at providing additional constraints on the seismogenetic faults at the southern termination of the Calabrian arc. Waveform similarities analysis allowed observing that ~ 45% of the whole dataset can be grouped into six different families of seismic events. Earthquake multiplet families are mainly located in the eastern part of the seismogenetic volume. We suggest that such a feature is responsive to the lateral lithological variations as highlighted by geology (at the surface) and P-wave seismic tomography (at depth of 10 km). Stress tensor inversions performed on FPSs indicate that the investigated region is currently subject to a nearly biaxial stress state in an extensional regime, such that crustal stretching occurs along both NW-SE and NE-SW directions. Accordingly, mesoscale fault geometries and kinematics analyses evidence that a younger normal faulting stress regime led to a tectonic negative inversion by replacing the pre-existing strike-slip one. Based on our results and findings reported in recent literature, we refer such a crustal stretching to mantle upwelling process (as evidenced by diffuse mantle-derived gas emissions) coupled with a tectonic uplift involving north-eastern Sicily since Middle Pleistocene. Moreover, seismic swarms striking the region would be related to the migration of mantle and sub-crustal fluids toward the surface along the complex network of tectonic structures cutting the crust and acting as pathways. [ABSTRACT FROM AUTHOR]

[Display omitted] • Offshore record of high-energy sedimentary events triggered by seismic activity. • Megaturbidites related to far field tsunamigenic earthquakes in the Hellenic Arc. • Megaturbidites triggered by Calabrian Arc subduction-type events. • Recurrence time of large plate-interface earthquakes is 2–3 ka. • The last subduction-thrust event dates back to 2.9 ka and this requires an update of the seismic hazard assessment in the region. The Calabrian Arc subduction-rollback system hosts seismogenic faults capable of generating earthquakes exceeding magnitude 7. Since earthquakes are the result of long-term geodynamic processes, documenting seismic activity during a sufficiently long time interval is of fundamental importance for hazard scenarios. Instrumental and historical data provide critical information on seismogenesis, but they cover time periods shorter than the recurrence times of large earthquakes, especially in areas with low deformation rates such as Calabria. If onshore paleoseismological studies are fundamental to compile earthquake catalogs, they are sometime affected by the relatively poor continuity of sedimentation in the subaerial environment. In this study we applied the paleoseismological approach to the submarine environment to reconstruct the record of high-energy sedimentary events triggered by seismic activity. We analyzed three gravity cores collected in disconnected sedimentary basins to reconstruct resedimentation processes during the Holocene, integrating inland information for a better assessment of tectonic activity and seismogenesis. Multiproxy analyses of the sedimentary record constrained by radiometric dating allowed reconstructing event stratigraphy and linking resedimented deposits to specific earthquakes. Onshore and offshore data allow to identify large-magnitude earthquakes in the central Calabrian Arc subduction system during the Holocene, with inferred epicenters located either along normal faults onshore and/or related to the slab dynamics. The turbidite record reveals 20 major events during the last 10 ka, with sources including crustal faults in Calabria (i.e. Lakes, Rossano and Cittanova faults). Analyses of sediment samples and high-resolution seismic reflection images allowed identification of different types of resedimented deposits during the last 30–50 ka. The basin-wide occurrence of three megaturbidites/homogenites suggests they are related to megatsunamis sourced by far field earthquakes along the Hellenic Arc. Megaturbidites with a more limited spatial extent are interpreted as subduction-type events in the Calabrian Arc, while thinner seismo-turbidites record the activity of crustal structures including faults onshore. Results suggest a recurrence time of 2–3 ka for major Calabrian Arc events that needs to be considered for a reliable hazard assessment in the Mediterranean region. [ABSTRACT FROM AUTHOR]

Probabilistic seismic hazard analysis (PSHA) are performed for routine applications using source models and ground motion models (GMMs) recommended by a government agency (e.g., US Geological Survey) or an expert panel (e.g., SHARE project). For important projects, site-specific PSHA involves critical analysis of GMMs and sources for the application region. We adopt the latter approach for a dam site in Calabria (southern Italy), a high seismic hazard region. We consider area sources as well as fault sources coupled with background zones, tailoring a model developed in the SHARE project for the subject site. We identify several problems with assigned maximum magnitudes for fault and in-slab subduction sources. We also add two sources not previously considered – the crustal Lakes fault and the Calabrian arc subduction interface. We select GMMs that are better constrained in the hazard-controlling range of magnitudes and distances than those typically used in prior Italian applications. Short-period median spectral accelerations at the 2475-year return period exceed those from prior SHARE studies by about 10–15%, and those from the Italian building code by amounts ranging from 15% to 96%. Despite the site being located in a region with finite faults capable of generating large events, the 2475-year hazard is dominated by source zones that allow for earthquakes directly beneath the site. [ABSTRACT FROM AUTHOR]

The Catanzaro Trough is a Neogene-Quaternary basin developed in the central Calabrian Arc, between the Serre and the Sila Massifs, and filled by up to 2000 m of continental to marine deposits. It extends from the Sant’Eufemia Basin (SE Tyrrhenian Sea), offshore, to the Catanzaro Basin, onshore. Here, onshore structural data have been integrated with structural features interpreted using marine geophysical data to infer the main tectonic processes that have controlled the geodynamic evolution of the western portion of the Catanzaro Trough, since Upper Miocene to present. The data show a complex tectonostratigraphic architecture of the basin, which is mainly controlled by the activity of NW–SE and NE–SW trending fault systems. In particular, during late Miocene, the NW-SE oriented faults system was characterized by left lateral kinematics. The same structural regime produces secondary fault systems represented by E-W and NE-SW oriented faults. The ca. E-W lineaments show extensional kinematics, which may have played an important role during the opening of the WNW–ESE paleo-strait; whereas the NE-SW oriented system represents the conjugate faults of the NW-SE oriented structural system, showing a right lateral component of motion. During the Piacenzian-Lower Pleistocene, structural field and geophysical data show a switch from left-lateral to right-lateral kinematics of the NW-SE oriented faults, due to a change of the stress field. This new structural regime influenced the kinematics of the NE-SW faults system, which registered left lateral movement. Since Middle Pleistocene, the study area experienced an extensional phase, WNW-ESE oriented, controlled mainly by NE-SW and, subordinately, N-S oriented normal faults. This type of faulting splits obliquely the western Catanzaro Trough, producing up-faulted and down-faulted blocks, arranged as graben-type system (i.e Lamezia Basin). The multidisciplinary approach adopted, allowed us to constrain the structural setting of the central Calabria segment. The joined onshore with offshore structural data analysis allowed us to image a more faithful geodynamic evolution of the Calabrian Arc, included in the wider geodynamic framework of the Mediterranean region Moreover, our results show the close correlation between the NE-SW and N-S normal fault systems and evidence of deformed Quaternary deposits. These findings are relevant to seismic hazard understanding in an area which is historically considered at the highest risk of earthquake and tsunami and where are present important infrastructures and cities. [ABSTRACT FROM AUTHOR]

The deep seismicity and lateral distribution of seismic velocity in the Central Western Mediterranean, point to the existence under the Alboran and Tyrrhenian Seas of two lithospheric slabs reaching the mantle transition zone. Gibraltar and Calabrian narrow arcs correspond to the slabs. Similarities in the tectonic and mantle structure of the two areas have been explained by a common subduction and roll-back mechanism, in which the two arcs are symmetrical end members. We present a new 3-D tomographic model at mantle scale for the Calabrian Arc and compare it with a recently published model for the Gibraltar Arc by Monna et al. ( 2013a ). The two models, calculated with inversion of teleseismic phase arrivals, have a scale and parametrization that allow for a direct comparison. The inclusion in both inversions of ocean bottom seismometer broadband data improves the resolution of the areas underlying the seafloor networks. This additional information is used to resolve the deep structure and constrain the reconstruction of the Central Western Mediterranean geodynamic evolution. The Gibraltar tomography model suggests that the slab is separated from the Atlantic oceanic domain by a portion of African continental margin, whereas the Calabrian model displays a continuous oceanic slab that is connected, via a narrow passage (~ 350 km), to the Ionian basin oceanic domain. Starting from the comparison of the two models we propose the following interpretation: within the Mediterranean geodynamic regime (dominated by slab rollback) the geometry of the African continental margin, located on the lower plate, represents a critical control on the evolution of subduction. As buoyant continental lithosphere entered the subduction zones, slab pull caused tears in the subducted lithosphere. This tectonic response, which occurred in the final stages of arc evolution and was strongly controlled by the paleogeography of the subducted plates, explains the observed differences between the Gibraltar and Calabrian Arcs. [ABSTRACT FROM AUTHOR]

The Calabrian Arc is a narrow subduction–rollback system resulting from Africa/Eurasia plate convergence. While crustal shortening is taken up in the accretionary wedge, transtensive deformation accounts for margin segmentation along transverse lithospheric faults. One of these structures is the NNW–SSE transtensive fault system connecting the Alfeo seamount and the Etna volcano (Alfeo–Etna Fault, AEF). A second, NW–SE crustal discontinuity, the Ionian Fault (IF), separates two lobes of the CA subduction complex (Western and Eastern Lobes) and impinges on the Sicilian coasts south of the Messina Straits. Analysis of multichannel seismic reflection profiles shows that: 1) the IF and the AEF are transfer crustal tectonic features bounding a complex deformation zone, which produces the downthrown of the Western lobe along a set of transtensive fault strands; 2) during Pleistocene times, transtensive faulting reactivated structural boundaries inherited from the Mesozoic Tethyan domain which acted as thrust faults during the Messinian and Pliocene; and 3) the IF and the AEF, and locally the Malta escarpment, accommodate a recent tectonic event coeval and possibly linked to the Mt. Etna formation. Regional geodynamic models show that, whereas AEF and IF are neighboring fault systems, their individual roles are different. Faulting primarily resulting from the ESE retreat of the Ionian slab is expressed in the northwestern part of the IF. The AEF, on the other hand, is part of the overall dextral shear deformation, resulting from differences in Africa–Eurasia motion between the western and eastern sectors of the Tyrrhenian margin of northern Sicily, and accommodating diverging motions in the adjacent compartments, which results in rifting processes within the Western Lobe of the Calabrian Arc accretionary wedge. As such, it is primarily associated with Africa–Eurasia relative motion. [ABSTRACT FROM AUTHOR]

Magma upwelling forming volcanic plumbing systems in back arc settings is typically controlled by extensional tectonic structures of the upper crust. Here we investigate this process in the area between the volcanic arc of the Aeolian Islands and the Calabrian arc (SE Tyrrhenian Sea) by integrating morpho-bathymetry and reflection seismic data with the outcomes of “Inverse 3D magnetic modeling” of previously gathered aeromagnetic data. Morpho-bathymetric data highlight the presence of a seamount ∼10 km offshore Capo Vaticano Promontory (eastern Calabria). This feature, named Capo Vaticano seamount is composed of a series of NE-trending ridges, the greatest of which (R1) is ∼12 km long, and 2.4 km wide, displays asymmetric flanks with a landward steep slope, oblique morphological steps and elongated NE-trending rims. The position of the R1 ridge summit fits the Reduced-to-the-Pole peak of a high-intensity magnetic anomaly straddling Capo Vaticano Promontory and its offshore prolongation. Seismic and bathymetric data highlight two extensional fault systems affecting the offshore of Capo Vaticano Promontory during the Plio-Pleistocene: (a) a Pliocene NW-trending, SW-dipping normal fault system, and (b) a Pleistocene NE-trending, SE-dipping normal fault system. The younger system is composed of a series of en-echelon branching normal faults bounding the eastern side of the R1 ridge. Aeromagnetic data modeling imaged a complex 3D-magnetized body below the R1 ridge exhibiting a sub-vertical conduit-like structure in the shallow part, and a NE-striking, sheet-like shape inclined by 45° in depth. The location of the sub-vertical conduit coincides with the summit of the R1 ridge. The magma uprising at the root of the volcano was controlled by the Pliocene NW-trending faults whereas its further upwards migration was ostensibly controlled by the Pleistocene NE-trending faults. Both fault systems are responsible for the high level of fracturing that likely favored the upward migration of magma. The younger extensional systems also controls the present-day, mantle derived, fluid escapes observed at the summit of the R1 ridge. Relying on seismic stratigraphic evidence as well as the normal polarity of the magnetic anomaly, the R1 ridge probably started to form during the Olduvai chron (early Pleistocene, 1.81–1.96 Ma). Accordingly, the Capo Vaticano volcano may represent the result of magmatic activity that predates the Aeolian volcanic arc. [ABSTRACT FROM AUTHOR]

In the epicentral area of the seismic swarm of the June–September 2011, at southern edge of the Calabrian arc in NE Sicily, very recent extensional motions remobilised two main NW–SE dextral faults. The extensional reactivation of strike–slip faults responded to a new regional dynamic, also evidenced by GPS and seismological data. The inverted structures are aligned at the margin of a wide crustal block that is moving apart from the rest of the island and is uplifting faster than the adjacent regions. The active faults terminate to the northwest at the intersection with a prominent NNE trending fault that represents the western boundary of the mobile block. The vertical displacement along this border exactly matches the difference in elevation of the marine terraces resting inside and outside the block, respectively. On the contrary, only part of differential displacement of the marine terraces was actually accommodated as cumulative motion along the two NW oriented inverted faults, across the southwestern boundary of the block. Amounts of the vertical displacement were distributed on distinct fault planes of the previous dextral shear belts. The widespread fracturing is also the best explanation for the seismic swarm of the 2011, whose epicenters spread on a discrete rock volume rather than concentrated along a single fault plane. The diffuse fracturing seems to represent a peculiar style of deformation, connected to the tectonic inversion of previous strike–slip shear zones. Seismic swarm also affects the northern termination of the Calabrian arc where active extensional deformation reactivated previous strike–slip faults. The similarity of the two regions suggests that seismic swarm can be peculiar of extensional belts developed on previous strike–slip shear zones, along which the pre-existing geometry favours the dispersion of the tectonic motion on a network of small linked fault planes. [ABSTRACT FROM AUTHOR]

The Calabrian Arc subduction complex, in the northern Ionian Sea, is facing directly the westward subducting Apulian Swell, a sliver of continental crust covered by about 8 km of Mesozoic and Tertiary carbonates. Deformation patterns of this southernmost foreland segment of the Adria plate, analized from marine geological/geophysical data include: 1) flexure/bending, under the load of the advancing Calabrian Arc wedge; 2) buckling in response to compression of the surrounding orogens (southern Apennines, Dinarides-Hellenides); and 3) roll-back and eastward retreat of the slab. In this work, a reprocessed dataset of marine seismic reflection profiles is used to determine the interplay between these tectonic processes during progressive advancement of the Calabrian Arc wedge since Pliocene times. Our analysis indicates that the wedge is presently affected by compressive tectonics along several fore-thrusts, forming an imbricate fan system. Conversely, the Apulian Swell affected by inherited and rift-related Permo-Triassic normal faults, shows transpressive and positive tectonic inversions and, in its southern portion, the effects of the Hellenic fold/thrust belt shortening. The interference between the Calabrian Arc and the Hellenic chain plays an important role in controlling the tectono-stratigraphic evolution of the Apulian Swell, which underwent bending and roll-back during a pre-middle Pliocene stage followed by buckling processes. Active extension observed in the hinge zone of the Apulian Swell between Calabrian Arc and the Hellenides might suggest recent reactivation of flexure and retreat. • The response of a subducting plate trapped between two converging orogenic wedge is investigated. • The interference of Calabrian Arc (CA) and Hellenic chain plays an important role in defining the tectono-stratigraphic evolution of the Apulian Swell (AP) in Central Mediterranean Sea. • The advancement of the CA wedge and the Hellenides transmitted compressive stress to the foreland, leading to a tectonic inversion of previous Mesozoic faults. • Compressive deformation at the AP-CA wedge contact zone suggests that the west-dipping AP is already part of the orogenic wedge. • Compressive tectonics is active also in the central sector of the AP implying that collisional tectonics can be propagated over long distances from plate boundaries. [ABSTRACT FROM AUTHOR]

The integrated interpretation of different types of data, consisting of a detailed Digital Terrain Model, field structural and morphotectonic observations, high resolution seismic data, seismological and Synthetic Aperture Radar interferometry information (vertical and horizontal movements), associated with a review of the available literature, has allowed to analyze the shallow expression of the regional-scale Petilia-Sosti Shear Zone (PSSZ). It is one of the major NW-trending tectonic lineaments affecting the Calabrian Arc and is characterized by a present-day tectonic and gravity-driven deformation. This study investigated the portion of the PSSZ between the offshore Crotone Peninsula, located along the Ionian sea of Calabria, and the central part of the Sila Massif. A complex tectonic history is documented since middle Miocene onward for the PSSZ. It consists of an alternation of sinistral and dextral transpressional and transtensional tectonic phases correlated with the geodynamic events occurred during the SE migration of the Calabrian Arc. The shallow expression of the investigated part of the PSSZ consists of a roughly 14 km wide, ca. 80 km long NW-trending tectonic zone including synthetic NW- to NNW-trending faults and N-NE antithetic minor structures. The main identified NW-trending faults, which show a development between 30 and 50 km, are the Sila and Lakes faults in the Sila Massif, and the Marcedusa-Steccato, Fosso Umbro and Tacina faults located in the SW part of the Crotone Basin and in its offshore area. Currently, the fault segments of the Sila Massif exhibit a prevailing normal kinematics with a left-lateral component, whereas a more complex geological framework occurs in the south-western part of the onshore-offshore Crotone Basin. The latter is dominated by gravity-driven movements, associated with the SE migration of the Crotone Megalandslide and with the regional uplift of Calabria, whereas normal kinematics with a small left-lateral component of movement, locally replaced by reverse/transpressional tectonics, was observed along the southern coast in the late Pleistocene deposits of the Le Castella marine terrace. The seismological data highlight that some strong earthquakes occurred in 1638, 1744 and 1832, with magnitude Mw between 5.7 and 6.8, might be associated with the Lakes, Fosso Umbro and Tacina faults respectively. In this frame, the PSSZ is proposed as a new potential NW-oriented active composite seismogenic source for the central-northern Calabria. • Identification of the major faults associated with the Petilia-Sosti Shear Zone (Calabria). • Currently aseismic and seismic tectonic activity along the Petilia-Sosti Shear Zone. • Normal kinematics with left-lateral component along the faults of the Sila Massif. • Gravity tectonics along the faults of the Crotone Basin-offshore Crotone Peninsula. • The Petilia-Sosti Shear Zone might represent a new composite seismogenic source. [ABSTRACT FROM AUTHOR]

Detailed mapping of geomorphological and biological sea-level markers around the Capo Vaticano promontory (western Calabria, Italy), has documented the occurrence of four Holocene paleo-shorelines raised at different altitudes. The uppermost shoreline (PS1) is represented by a deeply eroded fossiliferous beach deposit, reaching an elevation of ∼2.2 m above the present sea-level, and by a notch whose roof is at ∼2.3 m. The subjacent shoreline PS2 is found at an elevation of ∼1.8 m and is represented by a Dendropoma rim, a barnacle band and by a wave-cut platform. Shoreline PS3 includes remnants of vermetid concretions, a barnacle band, a notch and a marine deposit, and reaches an elevation of ∼1.4 m. The lowermost paleo-shoreline (PS4) includes a wave-cut platform and a notch and reaches an elevation of ∼0.8 m. Radiocarbon dating of material from individual paleo-shorelines points to an average uplift rate of 1.2–1.4 mm/yr in the last ∼6 ka at Capo Vaticano. Our data suggest that Holocene uplift was asymmetric, with a greater magnitude in the south-west sector of the promontory, in a manner similar to the long-term deformation attested by Pleistocene terraces. The larger uplift in the south-western sector is possibly related to the additional contribution, onto a large-wavelength regional signal, of co-seismic deformation events, which are not registered to the north-east. We have recognized four co-seismic uplift events at 5.7–5.4 ka, 3.9–3.5 ka, ∼1.9 ka and <1.8 ka ago, superposed on a regional uplift that in the area, is occurring at a rate of ∼1 mm/yr. Our findings places new constrains on the recent activity of border faults south of the peninsula and on the location of the seismogenic source the 1905 destructive earthquake. [ABSTRACT FROM AUTHOR]

We present a new seismic velocity model for the southern Apennines–Calabrian Arc border region with the aim to better define the crustal structures at the northern edge of the Ionian subduction zone. This sector also includes the Pollino Mts. area, where a seismic sequence of thousands of small to moderate earthquakes has been recorded between spring 2010 and 2013. In this sector a seismic gap was previously hypothesized by paleoseismological evidences associated with the lack of major earthquakes in historical catalogs. To perform the tomographic inversion we selected ca. 3600 earthquakes that have occurred in the last thirty years and recorded by permanent and temporary networks managed by INGV and Calabria University. Using for the first time the Local Tomography Software for passive tomography inversion (LOTOS hereinafter) to crustal analysis in southern Italy, we have computed the distribution of Vp, Vs, and the Vp/Vs ratio. The obtained velocity model, jointly evaluated with results of synthetic modeling, as well as with the hypocenter distribution and geological information, gives us new constraints on the geodynamical and structural knowledge of the study area. The comparison between the shallow tomography sections and surface geology shows good correlation between velocity patterns and the main geological features of the study area. In the upper crust a low-velocity anomaly of P- and S-waves is detectable beneath the Pollino Mts. area and seems to separate the Calabrian and southern Apennines domains, characterized by higher velocities. The distributions of high Vp/Vs ratio, representing strongly fractured rocks with likely high fluid content, clearly correlate with areas of significant seismicity. In the lower crust we detect a clear transition from high to low seismic velocities in correspondence with the Tyrrhenian coast of the study area, which may represent the transition from the thinner Tyrrhenian crust to the thicker one beneath Calabria. In this area, also characterized by a progressive detachment of a retreating lithospheric slab, the generation of a Subduction-Transform Edge Propagator (STEP) fault zone, that laterally decouples subducting lithosphere from non-subducting lithosphere in a scissor type of fashion, may have taken place. These conditions imply the existence of a kinematic decoupling which allows for differential movement between the Calabrian Arc and the southern Apennine chain. The low velocity anomaly separating the southern Apennines and the Calabrian Arc domain may be related to fluid upwelling occurring in correspondence with the northern edge of the Calabrian subducting slab. [ABSTRACT FROM AUTHOR]

Low-field anisotropy of magnetic susceptibility (AMS) analyses were performed on 532 samples collected in 36 (mostly lower Pliocene to lower Pleistocene) marine clay sites from the Crotone basin, a fore-arc basin located on top of the external Calabrian accretionary wedge. The Crotone basin formed since mid-late Miocene under a predominant extensional tectonic regime, but it was influenced thereafter by complex interactions with NW–SE left-lateral strike-faults bounding the basin, which also yielded post-1.2 Ma ∼30° counterclockwise block rotations. The basin is filled by continental to marine sediments yielding one of the thickest and best-exposed Neogene succession available worldwide. The deep-marine facies – represented by blue-grey marly clays gave the best results, as they both preserved a clear magnetic fabric, and provided accurate chronology based on previously published magnetostratigraphy and calcareous plankton (i.e. foraminifers and nannofossils) biostratigraphy. Magnetic susceptibility range and rock magnetic analyses both indicate that AMS reflects paramagnetic clay matrix crystal arrangement. The fabric is predominantly oblate to triaxial, the anisotropy degree low (<1.06), and the magnetic foliation mostly subparallel to bedding. Magnetic lineation is defined in 30 out of 36 sites (where the e12 angle is <35°). By also considering local structural analysis data, we find that magnetic fabric was generally acquired during the first tectonic phases occurring after sediment deposition, thus validating its use as temporally dependent strain proxy. Although most of the magnetic lineations trend NW–SE and are orthogonal to normal faults (as observed elsewhere in Calabria), few NE–SW compressive lineations show that the Neogene extensional regime of the Crotone basin was punctuated by compressive episodes. Finally, compressive lineations (prolate magnetic fabric) documented along the strike-slip fault bounding the basin to the south support the significance of Pleistocene strike-slip tectonics. Thus the Crotone basin shows a markedly different tectonics with respect to other internal and western basins of Calabria, as it yields a magnetic fabric still dominated by extensional tectonics but also revealing arc-normal shortening episodes and recent strike-slip fault activity. The tectonics documented in the Crotone basin is compatible with a continuous upper crustal structural reorganization occurring during the SE-migration of the Calabria terrane above the Ionian subduction system. [ABSTRACT FROM AUTHOR]

Abstract: The 28 December, 1908 Reggio Calabria and Messina earthquake (named after the two most damaged cities on the coasts of Messina Strait) was one of the strongest (MW 7.1) ever to occur in Italy, and was also followed by a tsunami that severely impacted the coasts of the Strait. Although there is general agreement that its epicentre is located offshore in the Messina Strait, the source fault has never been detected; a century-long question is therefore pending on the source of both the 1908 earthquake and tsunami. Within the ongoing debate on this subject, little attention has been given, so far, to morphological insights from high resolution bathymetric (multibeam) data, particularly as regarding the evidence of faults affecting the seafloor and the question of whether a submarine landslide may had been the cause of the tsunami. We aim to address this issue by presenting the results of a morpho-bathymetric study in the Messina Strait and surroundings, investigated by means of high-resolution swath bathymetry. The primary morpho-structural feature in this area is the axial channel of the Messina Canyon, towards which flow several tributary canyons that incise the steep continental slope on the Calabrian and Sicilian margins. These canyons carve deeply into a very narrow (almost lacking) continental shelf and merge laterally forming a continuous erosional margin rimming the Messina Strait. This giant, composite canyon environment is the locus of intense erosional and depositional processes that superimpose on active tectonic deformation, resulting in a complex geomorphology that hinders the distinction between tectonic and sedimentary features. Seafloor ruptures that may be linked to fault systems compatible with the source of the 1908 earthquake and tsunami could not be identified based from our morpho-bathymetric analysis; however, we provide evidence of several geomorphic features indicative of tectonic deformation in the Messina Strait, define the presence and distribution of submarine landslides, and evaluate their possible role as tsunami sources. [Copyright &y& Elsevier]

The development of Punta Stilo Swell (PSS), a submerged lobate-shaped promontory located in the Crotone-Spartivento Basin, is inferred to be closely linked to the Calabrian Arc kinematics since mid-Miocene onward. The latter consists of an alternation between long-term phases of subsidence related to forward migration of the Calabrian accretionary complex, and short-term compressional-transpressional phases, characterized by episodes of uplift and formation of regional unconformities, in a context of stopping or slowdown of Calabrian accretionary complex migration. In particular, the study area is supposed to have respectively experienced phases of compressional and extensional tectonics during late Messinian and early Pliocene, which likely produced a reactivation of inherited compressional and extensional structures. Late Pliocene/Pleistocene transtensional tectonics is documented along the offshore extension of the Soverato-Lamezia Fault Zone (SLFZ), in the N sector of the PSS. The resulting physiographic modifications associated with such compressional, extensional and transtensional tectonics is believed to have controlled the accumulation of the thick Plio-Pleistocene succession of the PSS. The northern continental slope is inferred to be the result of late Pliocene/Pleistocene transtensional tectonics occurred along the SLFZ, whereas the shelf break is considered the result of an early Pliocene extensional tectonics. The considerable steepness (>10°) of the southern and eastern continental slope of the PSS is associated with the late Messinian compressional tectonic activity and is marked by the occurrence of slope failure-associated events. • The PSS was generated from late Messinian to Pleistocene compressional, extensional and transtensional tectonics. • The tectonic evolution of the PSS is linked to the central Mediterranean geodynamics. • The present-day steepness of the slope setting is the expression of the late Messinian compressional tectonics. [ABSTRACT FROM AUTHOR]

Abstract: 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 12–15cm/kyr. Around 3.7–3.6Ma 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 50–60cm/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. 3.6Ma to ca. 3.2Ma, would have recorded a peculiar transitional period before further climatic deterioration and more drastic palaeoceanographic changes occurred around 3.1Ma, leading to cyclic sapropel deposition in the whole of the Mediterranean sea. [Copyright &y& Elsevier]

Abstract: 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 sediment analyses. The numerous seismogenic sources proposed in the literature during the past 15yr 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. Reappraising 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. [Copyright &y& Elsevier]

Abstract: Crustal earthquake focal mechanisms are investigated in the Calabrian Arc region, where the western Mediterranean subduction process is close to ending and the residual Ionian subducting slab affected by gravitational roll-back produces a strong variation of faulting regimes at shallow depth along the local section of the convergent margin. An updated database of earthquake focal mechanisms has been compiled by selecting the best-quality solutions available in the literature and in catalogs, and by adding 17 new solutions estimated in the present work. A total of 164 mechanisms are included in this database, 142 computed by waveform inversion and 22 by analysis of P-wave first motions from earthquakes with good network coverage and no less than 14 records. 60% of the solutions included in the database have never been used for regional-scale geodynamic investigations before the present study, and this makes the compiled database substantially new for our application. Focal mechanisms have been inverted for stress tensor orientations to obtain the principal stress axes over the study region. Results are compatible with three major tectonic domains subject to markedly different regional stresses along the arc. These three domains are separated by two transitional domains, which are located on top of the Ionian subducting slab edges and are likely forced in their horizontal transfer kinematics by the different tectonic regimes occurring in the adjacent major domains rather than by the regional tectonics. This along-arc differential tectonics is at least in part interpreted as the surface expression of the different deep mechanisms occurring in correspondence of the narrow Ionian slab and their lateral edges. Open tectonic questions are emphasized and proposed for future studies. [Copyright &y& Elsevier]

Abstract: The analysis of repeated high precision leveling observations during the last 40 years along lines of the Italian fundamental network allowed us to estimate very recent vertical movements in eastern Sicily and southern Calabria (Italy). The network is measured by the Italian Istituto Geografico Militare (IGM) and we have analyzed three leveling lines. Because of the lack of an absolute reference datum, we have conducted the analyses in terms of relative elevation changes compared to reference benchmarks. Although the processing of the different time series obtained from the high precision leveling has allowed us to estimate only relative rates, their extreme accuracy, together with the large extension of networks, makes this type of measurement fundamental for the estimate of recent vertical deformation. In addition, correlating instrumental and geological data makes it possible to identify active tectonic structures whose elastic strain accumulation could be responsible for vertical deformation. In particular, vertical motion can be related to the activity of a W-E trending fault separating the Catania Plain from the Hyblean Plateau in southeastern Sicily, a N-S trending normal fault occurring north of the Messina town and the NE-SW trending Scilla normal fault in south-western Calabria. The last two are located on the sides of the Messina Straits, an area of broad interest for the planning of the single-span bridge between Sicily and mainland Italy. [Copyright &y& Elsevier]

Abstract: The Southern Apennines, Calabro-Peloritane block, and Sicilian Maghrebides form a ~700km long orogenic bend, known as Calabrian Arc (Cifelli et al., 2007). The bending of this orogenic system was realized progressively through opposite-sense rotation of the two limbs, counterclockwise (CCW) in the Southern Apennines and clockwise (CW) in the Sicilian Maghrebides, synchronous to the Miocene-to-Present opening of the Tyrrhenian Sea. Despite the wealth of paleomagnetic data from the Southern Apennines, the main Miocene rotational phase still remains poorly constrained in time and, more importantly, data from the most internal paleogeographic domains of the belt are completely lacking. The Gorgoglione Formation, a middle Miocene piggy-back deposit of the Southern Apennines, unconformably resting over the internal Sicilide Unit, offers the unique opportunity to document the deformation pattern of the most internal units, and reconstruct the incipient tectonic phases leading to the formation of the Calabrian Arc. New paleomagnetic and biostratigraphic data from the Gorgoglione Fm. reveal a post-early Serravallian ~125° CCW rotation with respect to stable Africa. Such a large rotation, affecting the Gorgoglione Fm. (and consequently the underneath allochthonous Sicilide nappe) exceeds by ~45° the maximum mean CCW rotation previously reported for the Southern Apennines. We propose that the additional ~45° CCW rotation measured in the Sicilide Unit is the result of an earlier, late Miocene phase of deformation related to the onset of the Tyrrhenian Sea opening and affecting the most internal paleogeographic domains of the Southern Apennines. Our reconstructed tectonic scenario confirms and emphasizes the central role of the Ionian slab in the geodynamic evolution of the central Mediterranean. [Copyright &y& Elsevier]

Abstract: We present geophysical data integrated with the analysis of well-targeted sediment samples in order to contribute to a better understanding of fluid circulation in the Calabrian Arc accretionary wedge. Two cores (BS81/II 5 and BS81/II 10) collected on a swell in the hangingwall of the inner deformation front show upper Pleistocene mud breccias that include Cretaceous to Late Miocene rock fragments mechanically incorporated into the eruption deposit by the upward transport of overpressured fluids. An additional core (CALA 21) came from the summit of a topographic high in the footwall of the inner deformation front of the accretionary wedge and contains a mud breccia patchy/cloudy facies where sediment disturbance is caused by fluid expulsion. Integration of the entire data set provides evidences of the interplay among tectonics, fluid emissions and sedimentation, and enables the identification of two new volcanoes in the accretionary prism where overpressuring due to Pliocene and Pleistocene sediment accumulation and the evolution of active fault systems triggered fluid circulation and the formation of those structures. [Copyright &y& Elsevier]

Abstract: The Crotone Basin is the exposed part of a larger Neogene forearc basin developed in the Ionian Sea in the frame of the SE-ward migration of the Calabrian Arc, which led to the subduction of the Ionian lithosphere and the spreading of the Tyrrhenian back-arc Basin (central Mediterranean). Taking into account the geologic context that accompanied its accumulation, the Plio-Pleistocene part of the Crotone Basin succession is exceptionally well preserved, and consists of a suite of continental, paralic, shallow-marine and deep-marine deposits organized to form unconformity bounded stratal units that in turn compose two main tectono-stratigraphic cycles. The unconformities separating these units are well recognizable along the basin margin and tend to vanish basinwards, and they record phases of basin reorganization linked to large-scale tectonics. In particular, the basin evolution was characterized by a cyclic pattern consisting of an alternation between longer subsidence phases, that favored the accumulation of stratal units, and uplift phases that led to base-level falls and the generation of unconformities. These phases were strictly related to an alternation between active subduction of the Ionian lithosphere below the Calabrian Arc, accompanied by the spreading of the Tyrrhenian back-arc Basin and by extension and subsidence in the forearc basin, and regional-scale compressional and transpressional events, during which the Arc migration temporarily stopped. The younger uplift of the basin, started during middle Pleistocene and still active, was characterized by extensional tectonics, and its interplay with glacio-eustasy controlled the formation of marine terraces. Since the Plio-Pleistocene tectonic episodes affecting the Calabrian Arc during its SE-ward migration seem to be all recorded in the Crotone Basin, the recognition of their effects on the basin fill and their time constraint become both critical, representing a reference to develop a clearer picture on the complex evolution of the central Mediterranean. [Copyright &y& Elsevier]

Abstract: The coastal sector of Sant’Agata di Militello (north-eastern Sicily) is characterized by a flight of raised Middle-Upper Pleistocene marine terraces occurring at different heights with respect to present sea level. In particular, the geomorphological survey and the analysis of stereo-pairs of aerial photographs allowed to recognize at least five main orders of well preserved Quaternary surfaces and relative deposits mostly located at the hanging wall and at the footwall of the Pleistocene northwest-dipping Capo d’Orlando normal fault, which controlled the geomorphological evolution of the coastal area. The marine terraces show an overall good morphological continuity and are formed by marine platforms overlain by littoral deposits made up of yellow littoral sand and gravels in a sandy matrix. The continental sedimentary cover of the 3rd order terrace contains mammal-bearing deposits that were previously dated 200±40ka BP by isoleucine epimerization method, allowing to relate them to MIS 7.1 high-stand. In order to better define the whole terrace chronology, deposit samples were analyzed by Optically Stimulated Luminescence (OSL) methodology, a conventional SAR protocol used with sand-sized quartz. New datings, together with the detailed morphostructural analysis, allow to relate the 2nd and 4th order terraces to MIS 5.5 and 8.5, respectively, and to reconstruct the tectonic evolution of this coastal area, constraining the activity of the Capo d’Orlando fault. [Copyright &y& Elsevier]

Abstract: The Calabride nappe is the uppermost structural element of the Calabria–Peloritani Arc, it consists of a Variscan continental crust section intruded by late-Variscan granitoids, on which a Mesozoic syn-rift sedimentary cover was deposited. The deepest part of the Variscan continental section crops out in Northern Catena Costiera. The transition from crustal to mantle-derived rocks is often marked by gabbros. P–T estimates for gabbro emplacement have been calculated applying conventional thermobarometry and a mean crystallization temperature of about 800°C at pressures between ~0.46 and 0.65GPa has been determined. Gabbro emplacement occurs at the base of the crust, during a low-pressure granulitic stage that affected the country rocks at the end of an isothermal decompression. The gabbros can be classified as tholeiites with MORB affinity. In situ LA-ICP-MS U–Pb analyses have been performed on zircons from representative samples of gabbro. U–Pb concordia ages range from 224±4Ma to 296±6Ma. Two age populations of middle–early Permian and middle Triassic age, respectively, seem to document the magmatic activity responsible for gabbros intrusion. According to cathodoluminescent images and REE pattern of zircon, the early Permian age refers to a metamorphic inherited core. Lithospheric thinning and a positive thermal anomaly, related to the exhumation of the deepest portion of the continental lithosphere, can explain the post-Variscan metamorphic evolution of the Calabride lithosphere and the underplating gabbroic magmatism. Since the major episode of gabbro emplacement is Triassic, this event could be related to the continental rifting that led to the opening of the Jurassic Tethys and Alpine cycle. [Copyright &y& Elsevier]

Abstract: Subduction plays a fundamental role in plate tectonics and when interrupted it may trigger a series of geodynamic and sedimentary responses. Synchronous structural modifications recorded across the entire eastern Mediterranean region are dated to a relatively short period — early-to-mid Pleistocene. These deformations are documented within plates (e.g., Arabian, Sinai and African plates), along plate boundaries (e.g., Dead Sea and North Anatolian faults and Cyprus Arc), and in the Mediterranean basin. During the same period the northward subduction of the Sinai plate was interrupted when the Eratosthenes Seamount–Cyprus Arc collision initiated. Subduction–collision processes of the eastern Mediterranean serve as a unique modern analogue for similar settings worldwide. Understanding their association with accompanying neo-tectonic processes is therefore predominantly important. By fostering a detailed and comprehensive approach this research provides a coherent tectonic picture for the eastern Mediterranean early-to-mid Pleistocene tectonic transition in order to explore its triggering mechanisms. Since the Neogene convergence across the eastern Mediterranean was accompanied by Eurasian indentation by Arabia northward motion, westwards Anatolia escape and southwards Aegean propagation. This semi counterclockwise plate motion was temporarily interrupted by the incipient Seamount–Arc collision which is suggested here as a trigger of the early-to-mid Pleistocene tectonic transition. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: The present-day arcuate shape of the Calabrian Arc has been accomplished during Neogene and Early Pleistocene by large and opposite vertical axis rotations along the two arms of the Arc. Clockwise (CW) rotations have been systematically registered in Sicily and Calabria, whereas counterclockwise (CCW) rotations were measured in Southern Apennines. Such opposite vertical axis rotations ceased in the uppermost part of the Lower Pleistocene (about 1 Ma ago) along almost the entire Calabrian Arc and are not observed in the present-day GPS velocity field. The end of the Calabrian Arc bending during the Quaternary marks a decrease in the efficiency of the tectonic processes related to the long-lived subduction of the Ionian slab, which caused the halting of the back-arc opening in the Southern Tyrrhenian Sea. [Copyright &y& Elsevier]

Abstract: It is rarely possible to identify reverse faults that bring portions of substratum solid rock to lie above decomposed rock. Only where the differences between the fresh rock and weathered rock are very clear is it possible to recognise such faults. A “reverse profile” is defined as a slope profile in which fresh rock (granitoids) overlaps rocks which have been greatly altered by mature weathering (saprolite of granitoids). Such a profile occurs along the slopes of Molini Valley to the south of the village of Fabrizia (Calabria, southern Italy) and we interpret the morphological, mechanical and structural evidence as typical of a reverse fault. The mineral-petrographic analysis of the grus on the bed of the fault and of the cover of relatively fresh rock (Schmidt hammer 18–35) confirms that the granular framework can be attributed to subaerial alteration and not to mechanical deformation. The study area is located at the centre of the largest kinematic body of southern Calabria (the Serre massif-exclusively granitoids) until now considered to be only affected by extensional tectonics, creating high angle normal faults. In this area the tectonic processes, the thickness and spread of granitoid weathering mantles and the depth of the valleys, give rise to several landslides. These are generally translational slides with ample cut surfaces between the weathered body and the underlying fresh rock; as a consequence, very large deposits in the valleys can be found, mostly produced by debris flow processes. At the foot of the slopes around Fabrizia, coarse debris avalanches (with cobbles having a volume of over 0.3–0.4 m3) are occasionally observed, unless there is widespread development of a “reverse weathering profile” on the slopes above. [Copyright &y& Elsevier]

Abstract: 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 échelon 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 échelon 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. [Copyright &y& Elsevier]

Abstract: Geological and structural investigations have been integrated with the results of a study of anisotropy of magnetic susceptibility (AMS) carried out along the south-western side of the Calabrian Arc (NE Sicily; Lat.: 37°50′–38°00′N; Long. 14°57′–15°19′E). The results of this research suggest the occurrence of middle–upper Miocene passive clockwise rotations about a vertical axis. These rotations, superposed on pre-existing (Aquitanian) thrust and fold structures of the Calabrian Arc, have been identified by mapping of rotated (in plan view) regional traces of thrusts, beds, stretching lineations, fold axes and magnetic lineations evidenced by the AMS technique. The driving mechanism responsible for the origin of the recorded rotations could be sought in the geodynamic processes associated with WNW-dipping subduction and development of the Tyrrhenian Basin–Calabrian Arc–Apennines back-arc Basin–accretionary wedge system. According to previous models provided for this area, the southern margin of the mentioned arc-shaped system would be affected by clockwise rotations and by dextral transpression. Our results are consistent with the latter models, suggesting that middle–upper Miocene kilometre-scale clockwise rotations and folding occurred in northern Sicily as a result of dextral transpression along an E–W trend south of parallel 38°N. [Copyright &y& Elsevier]

Abstract: The study area is located in the south-eastern part of the Crati valley (Northern Calabria, Italy), which is a graben bordered by N–S trending normal faults and crossed by NW–SE normal left-lateral faults. Numerous severe crustal earthquakes have affected the area in historical time. Present-day seismic activity is mainly related to the N–S faults located along the eastern border of the graben. In this area, much seismically induced deep-seated deformation has also been recognised. In the present paper, radon concentrations in soil gas have been measured and compared with (a) lithology, (b) Quaternary faults, (c) historical and instrumental seismicity, and (d) deep-seated deformation. The results highlight the following: [(a)] There is no evidence of a strong correlation between lithology and the radon anomalies. [(b)] A clear correlation between the N–S geometry of radon anomalies and the orientation of main fault systems has been recognised, except in the southernmost part of the area, where the radon concentrations are strongly affected by the superposition of the N–S and the NW–SE fault systems. [(c)] Epicentral zones of instrumental and historical earthquakes correspond to the highest values of radon concentrations, probably indicating recent activated fault segments. In particular, high radon values occur in the zones struck by earthquakes in 1835, 1854, and 1870. [(d)] Deep-seated gravitational deformation generally coincides with zones characterised by low radon concentrations. In the studied area, the anisotropic distribution of radon concentrations is congruent with the presence of neotectonic features and deep-seated gravitational phenomena. The method used in this study could profitably contribute towards either seismic risk or deep-seated gravitational deformation analyses. [Copyright &y& Elsevier]

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. • Tectonic and sedimentary features in Calabrian Arc are strongly related. • Calabrian Arc sedimentary basins are linked to Alfeo Fault System (AFS) activity. • AFS is the shallow expression of the tear between European and Ionian plates. • Worldwide arc-shaped subduction zones develop similar side fault systems. [ABSTRACT FROM AUTHOR]

The Crotone Basin is a Neogene-Quaternary depocenter developed along the Ionian margin of Calabria, southern Italy. The basin opening was concomitant with the onset of spreading of the Tyrrhenian backarc Basin during late Serravallian and the subduction of the Ionian lithosphere below the Calabrian Arc. The adoption of modern sequence stratigraphic principles to subdivide the basin fill into stratigraphic sequences of different rank, bounded by subaerial unconformities, has allowed cycles of creation and loss of accommodation mainly related to tectonics to be recognized. In particular, an alternation between phases of basin subsidence, concomitant with spreading of the Tyrrhenian backarc Basin and forward migration of the Arc, and phases of compressional or transpressional tectonics, accompanied by basin uplift and stopping of Arc migration, are well recognizable in the basin fill, in particular for the late Messinian to late Pleistocene part of the succession. The present study highlights the effectiveness of the sequence stratigraphic method in basin analysis to decipher the effects of large-scale tectonic events on sedimentation and ultimately to reconstruct the geodynamic evolution of the central Mediterranean. • Relationships between tectonics and sedimentation related to the geodynamics of the central Mediterranean are recognized. • Two ranks of stratigraphic sequences and sequence boundaries are recognized. • The effectiveness of modern sequence stratigraphic principles to study the evolution of sedimentary basins is highlighted. [ABSTRACT FROM AUTHOR]