Inferences on the lithospheric structure of Campi Flegrei District (southern Italy) from seismic noise cross-correlation

Lithospheric Vs models are defined in the Campi Flegrei District (southern Italy) through the non-linear inversion of the group velocity dispersion curves of fundamental-mode Rayleigh waves extracted from ambient noise cross-correlations between two receivers, and the regional group and phase velocities of the Italian cellular lithospheric model (1 1 cells). Four paths are investigated, of which one (ISCHIA-MIS) across two adjoining cells. The distribution of Vs shows a pyroclastic covering with Vs increasing from 0.3–0.7 km/s to 2.1 km/s. It rests on a lava or carbonate basement, about 5–6 km thick, with VS increasing from 2.1 km/s to 3.1 km/s at about 2 km of depth and rising to about 0.6 km towards the island of Procida. A metamorphic layer is detected at an average depth of 7.7 km with Vs of 3.8–3.9 km/s, about 5 km thick, overlying a low velocity layer (Vs of 3.5 km/s) at about 11–12 km of depth. The Vs model along the ISCHIA-MIS path, as average of the models obtained by combining local and regional dispersion data of the two adjoining cells, is well consistent with the other paths. The Moho discontinuity is retrieved at about 23 km of depth with Vs of 4.2 km/s.