Abstract
A detailed 3D image of the Calabro-Ionian subduction system in the central Mediterranean was obtained by means of a seismic tomography, exploiting a large dataset of local earthquakes and computing algorithms able to build a dense grid of measure nodes. Results show that the slab is continuous below the southern sector of the Calabro-Peloritan Arc, but the deformation processes developing at its edges are leading to its progressive narrowing, influencing tectonics and magmatism at the surface, and with possible stress concentration in the tip zones. In the southwest, the deformation occurring at a free slab edge lead to propagation of a vertical lithospheric tear in the overriding plate, which extends along a NW-SE fault system (Aeolian-Tindari-Letojanni) up to about 30 km into the Ionian Sea; further southeast, the lithosphere appears only flexed and not broken yet. In the northeast, the slab seems to break progressively, parallel to the trench. Finally, northwest of Mt. Etna, the tomography highlights low VP that can be related to an upwelling of deep mantle material likely flowing laterally through a window opened by the complete slab detachment.
Highlights
Subduction processes have a great influence on the tectonic evolution and on the geologic architecture of a region, as well as on its seismicity and magmatism
Seismic tomography is the most effective method to explore the deep structure of subduction zones
We focus on improving the image of the Calabro-Ionian subduction system, by means of a local earthquake tomography (LET), in order to better understand the geodynamics and tectonics of the whole region
Summary
Subduction processes have a great influence on the tectonic evolution and on the geologic architecture of a region, as well as on its seismicity and magmatism. The present-day tectonic framework of the central-western Mediterranean arises from the evolution of this subduction process, which has been characterized by the rapid SE-ward rolling-back of the Ionian slab and by the opening of large back-arc extensional basins (i.e., Liguro-Provençal, Algerian, Alboran, and Tyrrhenian basins, Fig. 1a) This deformation produced lateral migration and relative rotation of orogenic wedges (e.g. refs[1,2]). We focus on improving the image of the Calabro-Ionian subduction system, by means of a local earthquake tomography (LET), in order to better understand the geodynamics and tectonics of the whole region For this goal, we considered a large dataset of about 20,100 earthquakes, encompassing both shallow and deep seismic events located in southern Italy and in the central Mediterranean, which was exploited to obtain a reliable 3D velocity structure and accurate hypocentre locations. We were able to investigate the large scale tectonic structures in unprecedented detail with respect to previous comparable tomographic studies (e.g. refs[7,18])
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