A 3D Vs model of the upper mantle beneath Italy: Insight on the geodynamics of central Mediterranean

We compute a high resolution Vs model of the upper mantle underneath Italy by inverting relative residuals of S-wave arrivals from teleseisms recorded at the Italian broad-band national seismic network. We also present a model of Vp/Vs perturbations obtained from similarly resolved P- and S-wave velocity models. The joint analyses of Vs and Vp/Vs models suggests that compositional variations concur with temperature variations to generate the observed velocity patterns, giving deeper insight into the upper mantle structure. The investigation of coherent high Vs and high Vp anomalies permits a comprehensive picture of the main oceanic domains involved in the puzzling subduction system of the central Mediterranean. Slab windows and tears developed in the Ionian slab are highlighted by regions of low Vp, low Vs and high Vp/Vs anomalies. The Adria continental lithosphere is characterized by high Vp, high Vs and low Vp/Vs anomalies that trace the sinking of eclogitized material underneath the Apennines and the Eastern Alps chains. The overall tomographic results yield the development of a new conceptual model for the Alps and Apennines formation, in which three basic processes occurred in different time and different locations all around the Alpine–Apennines system: continental collision, slab break-off and delamination of the upper-plate lithosphere.

► We present the first S-wave model for the central Mediterranean upper mantle.
► High Vp/Vs mantle anomalies highlight tears in the retreating Ionian slab.
► High Vs, low Vp/Vs regions in the uppermost mantle point to continental delamination.