3-D SV-Wavespeed Structure of Northern Europe Inferred from Rayleigh Waveform Tomography

Abstract

In this thesis we present a three-dimensional (3-D) seismic SV-wave speed model for the upper mantle beneath Northern Europe derived from the analysis of fundamental mode Rayleigh waveforms. Selecting recordings with centroid moment tensor (CMT) information from the dataset that has been extracted by Weidle and Maupin (2008), we employed an approach based on a two-stage inversion. The first step is waveform inversion using the technique of Cara and Leveque (1987), which utilizes secondary observables derived from narrow-band filtered cross-correlograms to perform waveform fitting between the recorded and synthetic surface wave seismograms. After the application of a series of model robustness tests on the resulting sets of depth-dependant path-averaged models, only 250 of them are retained for further processing. The second step of the inversion is a tomographic process applied on the one-dimensional (1-D) path-averaged models to retrieve the lateral variation in SV-wave speed. Consequently, this provides the 3-D structure for SV-wave speed distribution throughout the upper mantle beneath Northern Europe.

The constructed 3-D model is able to image the first order tectonic features in Northern Europe quite well. The low velocity in the Mid-Atlantic ridge, the high velocity in the East-European craton and the Trans-European suture zone are very well imaged. In addition to this, our model in general compares well with other models constructed for the same region.