USING SEISMIC DATA TO UNDERSTAND RIFT EVOLUTION IN MAGMA POOR RIFTS. AN EXAMPLE OF THE ALBERTINE RIFT

Studies have so far shown that strain within fault populations in the East African Rift System (EARS) is supported by the mechanical and thermal effects of magma intrusion and fluid-driven weakening. However, the western branch of the EARS is amagmatic and some studies have shown that pre-existing structures like lithospheric fabrics play a critical role in the strain localization process. There have been very few investigations into the overall development of the fault system in the Albertine rift in the western branch. Investigation into how these faults form reveals that they develop at depths along the fault line. In this study, we determined strain rates within the fault systems beneath the sediments based on 2D and 3D reflection seismic data from the Albertine -Rhino Graben. These were extracted and loaded from different seismic lines and multiple throws were calculated. Our results suggest that border faults accommodated the maximum strain in the Albertine rift, this is based on maximum throws of up to about 5km. However, this idea only works when the faults are covered in sediment. These results suggest that strain localization is accommodated by rift border faults and there is no suggestion of strain migration from border to rift axis. During asthenospheric upwelling, thinning and brittle deformation, movements along the border faults controlled the interaction between upper crustal thinning and surface brittle deformation.