Upper mantle structure of the British Isles from Rayleigh wave dispersion

Abstract

Fundamental mode Rayleigh wave phase velocities have been measured over the period range 15‐140 s for two paths within the British Isles, from southern Scotland (ESK) parallel to the trend of the Caledonides to south‐west Ireland (VAL), and from ESK to southern England (WOL). Errors generated in these observations during the processing sequence have been examined in detail, and empirically derived uncertainty bounds have been placed on the data. Inversion of the dispersion velocities to S‐wave velocity‐depth profiles using the Hedgehog technique yields a set of models for the Caledonides path (ESK‐VAL) which are similar to typical continental aseismic platforms, with a well‐developed low‐velocity channel of shear velocity, Vs, 4.2‐4.4 km s‐1. Lithosphere thickness is in the range 110‐190 km with a sub‐Moho velocity of 4.525‐4.6 km s‐1. Although the lithosphere along the other path (ESK‐WOL) has comparable velocities it must be at least 140 km thick: beneath this the low‐velocity channel is less pronounced (Vs > 4.4 kms‐1) or absent. Hence this profile appears distinct from that for the Caledonides and is significantly different to that for the North Sea region. Instead it is shield‐like and is not distinguishable from profiles for the Baltic Shield and parts of Hercynian France. Copyright © 1981, Wiley Blackwell. All rights reserved