Mark van der Meijde¹, Hanneke Paulssen², Islam Fadel¹ and Tarzan Kwadiba³, (1)University of Twente, Enschede, 7500, Netherlands, (2)Utrecht University, Dept. of Earth Sciences, Utrecht, Netherlands, (3)Principal Geophysicist 1 & Head of Geophysics Division, Botswana Geoscience Institute, Lobatse, Botswana