Velocity structure of the western Mediterranean from inversion of P-wave traveltimes

Abstract

residuals along ray paths with a penetration depth of 70-300km in the western Mediterranean. The inversion procedure is based on the Backus-Gilbert formalism for linear inversion of traveltime data, extended for 2-D and 3-D inhomogeneous media by Yanovskaya (1980) and Gobarenko & Yanovskaya (1983). P-wave traveltime residuals are derived along 87 ray paths from analyses of the ISC bulletin data. The P-wave velocity patterns constructed after the inversion, for the depth interval 50-300 km, are characterized by well-pronounced low-velocity zones in the French Massif Central, the Tyrrhenean Sea and the Ligurian Sea and by a high-velocity zone in southern Italy and Sicily. These patterns are discussed in terms of geophysical data (regional isostatic anomalies, heat flow) for the region. Several possible mechanisms (mantle convection, compositional changes in the low-velocity layer) causing the obtained correlation between different geophysical fields are discussed.