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The role of tectonics in the Neogene-Quaternary evolution of the forearc basin, between the Serre and Aspromonte Massifs, located in the southern Calabria, is widely documented in the exposed sedimentary successions. The structuration of these different basins is due to the southeastward migration of the Calabrian Terranes, which led to the subduction of the Ionian lithosphere and the spreading of the Tyrrhenian back-arc basin. The area is dominantly displaced by two NW–SE and NE–SW oriented regional fault systems. These fault systems were active during the infilling of the Neogene-Quaternary basins, and represent complex tear fault systems that accommodated stress generated in the accretionary prism during the subduction of the Ionian lithosphere. Furthermore, these structures play a relevant role as part of recent seismotectonic processes, which controlled the Late Quaternary geodynamic evolution of the area.

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 Crotone Basins (CB) (Zecchin et al., 2013 and references therein) is located in the eastern sectors of the Sila Massif. The CB depicts the Neogene-Quaternary foreland basin of central Mediterranean region. The study area is influenced by different set of NW-SE major transcurrent faults and their antithetic lineaments which show alternating episodes of transtensional and transpressional faulting. Southwestern sector of the basin was characterized by three main fault patterns: 1) Active since Serravallian, NW-SE oriented faults bordering the CB to the west and with a left-lateral strike slip kinematics at the first stage. This transtensional phase has produced the basin opening, filled by coarse-grained, sand, clay and evaporitic deposits. 2) To the central part of the study area, Miocene deposits was displaced by NNW-SSE and NE-SW oriented faults, this pattern displays a dextral transpressional kinematic which seems to replace extensional kinematic giving rise to local inversion of former basins.3) The CB experienced a new extensional phase along N-S or NNW- SSE oriented normal faults, starting from the Middle Pleistocene period.

Italy is one of the most seismically active regions in the central Mediterranean and one of the countries with the longest record of historical earthquakes in the world. Over the last decades the scientific community has recognised the value of historical data when used to constrain modelling tools in hazard analyses. This is the case of the destructive 1905 Calabria (South Italy) earthquake, followed by a tsunami and by many secondary effects on the environment observed both inland and offshore. Recently acquired geophysical data allowed to identify an active normal fault, named Sant'Eufemia Fault, located nearshore in the Sant'Eufemia Gulf (SE Tyrrhenian sea), considered the most probable seismogenic source of the 1905 earthquake and capable to trigger future events. In this paper we perform a scenario-based deterministic analysis for an earthquake resulting from the rupture of the Sant'Eufemia fault (SEF) and a preliminary potential risk analysis. After defining source parameters compatible with the 1905 earthquake (ca. 40 km fault length and ca. 2.3 m slip, Mw 6.9), KF-analysis and tsunami simulations are carried out and modelling results are compared against historical available data. The obtained results allow one to border areas in central Calabria that are most exposed to geohazard deriving from the analyzed fault. Some of these areas happen to be zones with intense economic/touristic and urban development, which calls for the need to integrate the ongoing development plans with adequate programs of risk mitigation and prevention.

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.