Transient Electromagnetic and Magnetotelluric Survey Across Southern Kenya Rift Valley: prelimenary results

The Kenya Rift Valley has long been recognised as a "classic" continental rift, and has been extensively studied by verious workers using a variety of techniques. In early 1995 an integrated TEM and MT profile was recorded across southern Kenya extending from Lake Victoria to Chyulu Hills to obtain better understanding of lithospheric structure and rifting process in the southern part of Kenyan rift and its flanks, including the Quaternary volcanic field of the Chyulu Hills. Joint TEM and MT data (102_10.2 sec) were collected at 20 sites across southern Kenya. The MT data have been corrected for static shift effects using the TEM data. The prelimenary result of TEM-constrained 2-D MT inversion indicates several interesting features across three different tectonic zones: (i) Outside the Rift Valley, enhanced conductivities are suggested at both crustal and mantle depths extending away from the eastern and western flanks. (ii) Within the main Rift zone, is seen an uppermost,S km thick, highly conductive horizon. (iii) In the volcanic area of the Chyulu Hills, 150 km east of the Rift Valley, a zone of high conductivity extending from upper crustal to mantle depths is suggested.