Shear wave velocity structure of the Bushveld Complex, South Africa

In this study, upper crustal structure of the Bushveld Complex (BC) is investigated. The BC is a prominent layered igneous mafic intrusion located within the northern part of the Kaapvaal Craton, South Africa. Past studies suggest that the mafic outcrops of the western and eastern limbs of the BC may be continuous and connected at depth. The principal objective of this study is to map out the continuity and connectivity of mafic units of the BC in areas without surface exposure using high frequency Rayleigh wave tomography and the joint inversion of high frequency receiver functions and short period Rayleigh wave group velocity. Event-station, group velocities have been measured for 201 local and regional earthquakes. These earthquakes were recorded by 42 broadband stations selected from the temporary SASE (Southern African Seismic Experiment) network and two broadband stations each belonging to the GSN (Global Seismic Network) and SANSN (South African National Seismograph Network). Most of the earthquakes occurred within deep gold mines to the south of the BC and within mines within the BC itself. Results of the lower crust of the BC confirm the presence of about 5 km of crustal thickening under the BC and suggest that the upper crust in the middle of the BC may have high velocities indicative of mafic rock layers near the surface.