Upper mantle discontinuities beneath South Africa

Abstract

This dissertation investigates the upper mantle discontinuities beneath South Africa by analysing seismic waves converted from p to Sv recorded at an array of broad band seismometers. Events, with desirable characteristics recorded at each station are transformed to a suitable coordinate system, normalised, and stacked to enhance the weak converted phases. Additional low pass filters are also applied to improve the signal to noise characteristics of the data. No data suitable to processing were found for stations outside the Kaapvaal craton Despite additional problems related to the application of sub-optimum numerical routines to a limited data base, by combining results with those from an independent study two models were derived for the '400 km' and '670 km' discontinuities beneath the Craton. Models for the '670 km' discontinuity accord with a simplified global earth model while models for the '400 km' discontinuity indicate the presence of a low shear velocity layer not supported in a global earth model. Addltlonal broad band seismic data must be acquired to investigate this phenomenon further.