UPPER MANTLE STRUCTURE UNDER WESTERN-EUROPE FROM FUNDAMENTAL AND HIGHER MODE SURFACE-WAVES USING THE NARS ARRAY

A generalized inversion of a new data set, consisting of surface wave phase velocities and Sn traveltimes, has resulted in a new shear velocity and density model for the west‐European platform (WEPL 2). the surface wave phase velocity data set consists of fundamental and higher mode (mode 1‐6) measurements from 25 to 70mHz, using the Network of Autonomously Recording Stations (NARS) array, which was specifically designed for higher mode surface wave measurements. the Sn traveltime data set consists of ISC readings for selected European events. Major features of WEPL 2 are a high‐velocity lid of 80‐140 km depth, underlain by a pronounced low‐velocity zone between 160 and 220 km depth. the transition zone (400‐650 km depth) is characterized by high shear velocities with respect to PREM. the density shows a positive gradient from 60 to 140 km depth, followed by an approximately constant value down to 400 km depth. A model for the Baltic shield (SCSH 2) is obtained by combination of Nolet's (1977) higher mode phase velocity data set for western Europe including the Baltic shield and the present phase velocities for the platform. This shield model shows an absence of the low‐velocity layer and low shear velocities in the top of the transition layer with respect to WEPL 2. Density, although less well resolved, shows lower values for the shield structure between 200 and 350 km depth. Copyright © 1990, Wiley Blackwell. All rights reserved