Receiver function structure beneath three southern Africa seismic broadband stations

Abstract

The shear wave velocity structure beneath three southern African stations, Lusaka (LSZ), Lobatse (LBTB) and Boshof (BOSA) were estimated using the time domain inversion of stacked teleseismic receiver functions. Broadband teleseismic 3-component waveform data were used in a source equalisation procedure to estimate radial and transverse receiver functions for each station. The radial receiver functions were stacked according to the following criteria, an azimuthal interval of ±15°, similar ray parameter and shape. For the shield-based stations BOSA and LBTB simpler receiver functions than for LSZ, which is located in the Irumide belt, were obtained. The lateral variation in receiver functions with azimuth as observed at each station stems from lateral heterogeneities beneath each station. The velocity models were presented as P wave velocity models. From these models, the crust mantle transition zones beneath LSZ and BOSA were determined at depths of about 37–44 km and 34–38 km respectively. For LBTB, the northeast quadrant velocity model displayed a clear mantle-continent transition zone in the depth range 40–45 km, whilst the Moho depth in the southern quadrants is not as clear. Beneath all the stations, we observed a low velocity zone, which appears to correlate with the cratonic velocity structure. This feature is consistent with crustal structure results obtained in other cratonic or shield-based crustal studies. The results in this study contribute crustal structure information, which has been lacking at BOSA, LBTB and LSZ.