Upper mantle structure below the European continent: Constraints from surface-wave tomography and GRACE satellite gravity data

Abstract

We here exploit fundamental mode Rayleigh and Love seismic wave information and the high resolution satellite global gravity model GGM02C to obtain a 1° × 1° 3-D image of: (a) upper-mantle isotropic shear-wave speeds; (b) densities; and (c) density-vS coupling below the European plate (20°N–90°N) (40°W–70°E). The 3-D image of the density-vS coupling provides unprecedented detail of information on the compositional and thermal contributions to density structures. The accurate and high-resolution crustal model allows us to compute a reliable residual topography to understand the dynamic implications of our models. The correlation between residual topography and mantle residual gravity anomalies defines three large-scale regions where upper mantle dynamics produce surface expression: the East European Craton; the eastern side of the Arabian Plate; and the Mediterranean Basin. The effects of mantle convection are also clearly visible at: (1) the Eastern Sirt Embayment; (2) the West African Craton northern margins; (3) the volcanically active region of the Canarian Archipelago; (4) the northern edge of the Central European Volcanic Province; and (5) the Northeastern part of the Atlantic Ocean, between Greenland and Iceland. Strong connections are observed among areas of weak radial anisotropy and areas where the mantle dynamics show surface expression. Although both thermal and additional dependencies have been incorporated into the density model, convective down-welling in the mantle below the East European Craton is required to explain the strong correlation between the estimated negative mantle residual anomalies and the negative residual topography.