Publications

Delvaux, D.,  Kervyn, F. & Temu, E.B. 2011. ‘Sismotectonics and active tectonics in the Western rift branch, Tanzania: a review’. OAGS-IGCP project 601 Seismotectonics and Seismic Hazards of Africa, Windhoek, Sept.26-29 2011 / AfricaArray workshop, Johannesburg, Novemver 20-21, 2011. Book of abstracts.

Conference abstract

The Rukwa region in the Western Highlands of Tanzania is one of the most seismically active segments of the western branch of the East African rift system. This region contains evidence for past strong earthquakes as recorded in the neotectonic morphology, paleoseismic trenches and outcropping recent lacustrine deposits in the paleo-shorelines and abandoned floor of Lake Rukwa. It was hit by an Ms 7.4 earthquake on December 13, 1910. Together with the Mw 7.1 May 20, 1990 Sudan earthquake and the Mw 7.0 February 22, 2006 Machaze earthquake in Mozambique, they are the only three M >= 7.0 events instrumentally recorded yet in the East African Rift. The Ms 7.4 Rukwa earthquake was part of a seismic crisis that lasted about 20 years and affected the Ufipa Plateau between Lakes Tanganyika and Rukwa and the Mbozi block, between Lakes Rukwa and Malawi. The epicentre of the Ms 7.4 Rukwa earthquake was located near Sumbawanga town along the Kanda normal fault system that cut longitudinally the Ufipa plateau. Lake Rukwa is also in an old but still active rift graben, with active faulting affecting its lake floor, far from the major border faults. In the Katavi paleo shore line at the north-western extremity of Lake Rukwa, morphostructural analysis and paleoseismic trenching evidenced also an active sismogenic fault. The Songwe depression with forms the southern extremity of the Rukwa depression has been affected since 300 Ka by intense tectonic activity in a transtensional context that controlled the deposition of the Songwe travertine deposit, caused pull-apart deformation of the former lacustrine deposits and was responsible for soft sediment deformation in the late Quaternary lake beds.