Magnetotelluric sub-basalt imaging of the Omo Basin, Turkana Rift, South-west Ethiopia

Abstract

31 magnetotelluric (MT) sites were occupied over the eastern Omo basin in southwest Ethiopia. Robust processing and 3D modelling indicates a N-S geoelectrical strike, in agreement with the geological strike, with up to 4km of sediments in the southern part of the basin, but no more than 2km in the northern part, underlain by more resistive material, assumed to be basement. Local resistive features in the near surface are possibly volcanic intrusions in the sediments. A more extensive resistive feature beginning at about 1km depth is sensed to the west of our most westerly sites. It coincides with the eastern edge of a linear, N-S feature seen on satellite imagery, where surface Quaternary volcanics have been observed, but could alternatively be sandstone, consistent with the basin consisting of two half-graben structures.