Neotectonics of the Central Kenya Rift

The Central Kenya RIft (CKR) is one of the fastest deforming sections of the Eastern African Rift System (EARS). Extensive tectonic research has been performed on the rift in northern and southern Kenya, but the modern tectonic geomorphology of the CKR remains understudied. Existing fault maps show a change in the orientation of the EARS within the CKR, although faults have not been mapped in detail with modern techniques. Despite the numerous fault scarps that offset the rift floor, few large earthquakes have been recorded in the recent past, with the exception of a M_S 6.9 event in 1928. Maturing rifts demonstrate a shift from border fault seismicity to increased aseismic deformation dsitributed along intra-rift faults. This study aims to map active fault scarps within the CKR to better understand the modern tectonics, which may give insights into seismic hazard for an area with a high population growth rate. Rigorous examination of the high resolution TanDEM-X Digital Elevation Model (DEM) was used to formulate a digital fault database, which includes attributes about individual fault lengths and orientations. The NNW-SSE orientated CKR represents an intersection between NNE-SSW orientated EARS rifts to the north and south, and older NNW-SSE orientated structural fabrics. While the CKR itself shows a traditional mature rift morphology containing a developed inner graben with recent volcanism, the junction between the CKR and Northern Kenya Rift appears to be less mature. The 1928 earthquake, which occurred along a border fault in this junction, challenges the theory of axial strain concentration in an aging rift. Calculations on the balance of extension accommodated by larger border faults vs younger intra-rift grid faults allows for the possibility of continued border fault slip. The lack of large earthquakes in the CKR itself suggests an aseismic model to describe deformation, while seismic hazard appears to be greater in the junctions between rift segments of alternate orientations.