3-D shear wave velocity model of the lithosphere below the Sardinia-Corsica continental block based on Rayleigh-wave phase velocities

Abstract

Rayleigh-wave dispersion curves from both ambient noise and teleseismic events allow us to provide the first high-resolution 3-D shear wave velocity (VS) model of the crust and upper mantle below the Sardinia-Corsica microplate, an important continental block for understanding the evolution of the central-western Mediterranean. For a wide range of periods (from 3 to ∼30 s), the phase velocities of the study area are systematically higher than those measured within the Italian peninsula, in agreement with a colder geotherm. Relative and absolute variations in the VS allow us to detect a very heterogeneous upper crust down to 8 km, as opposed to a relatively homogeneous middle and lower crust. The isosurface at 4.1 km s-1 is consistent with a rather flat Moho at a depth of 28.0 ± 1.8 km (2σ). The lithospheric mantle is relatively cold, and we constrain the thermal lithosphere-asthenosphere boundary at ∼100 km. We find our estimate consistent with a continental geotherm based on a surface heat flow of 60 mW m-2. Our results suggest that most of the lithosphere endured the complex history of deformation experienced by the study area and imply, in general, that deep tectonic processes do not easily destabilize the deeper portion of the continental lithosphere, despite leaving a clear surface signature.