A B S T R A C TIn order to characterize and quantify the Middle-Late Quaternary and ongoing deformation within the Southern Aegean forearc, we analyse the major tectonic structures affecting the island of Crete and its offshore. The normal faults typically consist of 4-30-km-long dipslip segments locally organised in more complex fault zones. They separate carbonate and/or metamorphic massifs, in the footwall block, from loose to poorly consolidated alluvial and colluvial materials within the hangingwall. All these faults show clear evidences of recent re-activations and trend parallel to two principal directions: WNW-ESE and NNE-SSW. Based on all available data for both onland and offshore structures (morphological and structural mapping, satellite imagery and airphotographs remote sensing as well as the analysis of seismic profiles and the investigation of marine terraces and Holocene raised notches along the island coasts), for each fault we estimate and constrain some of the principal seismotectonic parameters and particularly the fault kinematics, the cumulative amount of slip and the slip-rate. Following simple assumptions and empirical relationships, maximum expected magnitudes and mean recurrence periods are also suggested. Summing up the contribution to crustal extension provided by the two major fault sets we calculate both arc-normal and arcparallel long-term strain rates. The occurrence of slightly deeper and more external low-angle thrust planes associated with the incipient continental collision occurring in western Crete is also analysed. Although these contractional structures can generate stronger seismic events (M ≈ 7.5.) they are probably much rarer and thus providing a minor contribution to the overall morphotectonic evolution of the island and the forearc. A comparison of our geologicallybased results with those obtained from GPS measurements show a good agreement, therefore suggesting that the present-day crustal deformation is probably active since Middle Quaternary and mainly related to the seismic activity of upper crustal normal faults characterized by frequent shallow (<20 km) moderate-to-strong seismic events seldom alternating with stronger earthquakes occurring along blind low-angle thrust planes probably ramping from a deeper aseismic detachment (ca. 25 km). This apparently contradicting co-existence of juxtaposed upper tensional and lower compressional tectonic regimes is in agreement with the geodynamics of the region characterised by continental collision with Nubia and the Aegean mantle wedging.
We here propose a new kinematic picture of central Sicily based on the results of detailed field mapping of the region, combined with structural analyses and the interpretation of the available literature subsurface data. Our study focused on the tectonic boundary of a structural depression, the Caltanissetta Trough, which is now filled with allochthonous terrains resting on the deep-seated inverted African palaeomargin units. Our data refer to the tectonosedimentary evolution of the thrust-top basins, from Late Tortonian to Quaternary times. The study points out the occurrence of regional E–W-oriented dextral shear zones, cutting the NE-oriented trends of the thrust belt. This new evidence would confirm the major role of the E–W trend in the tectonic inversion of the external portions of the Africa palaeomargin in Sicily. Our results could contribute to a better understanding of the location in Sicily of the tectonic lineaments accommodating the hundreds of kilometres of lateral displacement, caused by the Late Miocene–Quaternary Tyrrhenian Basin opening to the north of the island.
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