Abstract
Based on multidisciplinary data, including seismological and geodetic observations, as well as seismic reflection profiles and gravity maps, we analysed the pattern of crustal deformation and active tectonics in the Sicily Channel, a key observation point to unravel the complex interaction between two major plates, Nubia and Eurasia, in the Mediterranean Sea. Our data highlight the presence of an active ~ 220-km-long complex lithospheric fault system (here named the Lampedusa-Sciacca Shear Zone), approximately oriented N–S, crossing the study area with left-lateral strike-slip deformations, active volcanism and high heat flow. We suggest that this shear zone represents the most active tectonic domain in the area, while the NW–SE elongated rifting pattern, considered the first order tectonic feature, appears currently inactive and sealed by undeformed recent (Lower Pleistocene?) deposits. Estimates of seismological and geodetic moment-rates, 6.58 × 1015 Nm/year and 7.24 × 1017 Nm/year, respectively, suggests that seismicity accounts only for ~ 0.9% of crustal deformation, while the anomalous thermal state and the low thickness of the crust would significantly inhibit frictional sliding in favour of creeping and aseismic deformation. We therefore conclude that a significant amount of the estimated crustal deformation-rate occurs aseismically, opening new scenarios for seismic risk assessments in the region.
Highlights
Comparisons between seismological and geodetic deformation-rates may provide significant insights for seismic hazard assessment in tectonically active regions
In southern Sicily, seismicity is mainly clustered in the Hyblean plateau and the Belice area, and marks the presence of active tectonic structures which were the site of historical earthquakes (Fig. 2a)
Our statistical evaluation of the deformation-rate budget for the Sicily Channel was focused on the area delimited by the blue polygon in Fig. 2a, which was chosen in relation to the distribution of continuous GPS stations
Summary
Comparisons between seismological and geodetic deformation-rates may provide significant insights for seismic hazard assessment in tectonically active regions. Starting from the Late Miocene and mostly during the Early Pliocene, a lithospheric-scale continental rifting occurred in the central part of the Pelagian b lock[19], with a subsequent phase (Late Pliocene–Pleistocene) characterized by a magma-assisted e xtension[20] This rifting process led to the development of NW–SE-trending tectonic depressions (e.g., Pantelleria, Linosa and Malta troughs), bordered by crustal normal faults with variable throws[21] (Fig. 1b). The magmatic activity started in the Nameless Bank in the Late Miocene and continued to the present-day close to Pantelleria and to the south-eastern wedge of the Graham Bank[12,24] and is characterized by a wide spectrum of volcanic rocks with tholeiitic, alkaline and peralkaline affinities[25] (see details in Supplementary Information)
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