Deformation pattern of the March April 2023 mudflow in Ilemera Gwanseli Muleba Tanzania and its relevance to neotectonic activity along the western branch of the East African Rift System

Abstract

The March–April 2023 mudflow event in Ilemera-Gwanseli, Muleba, west of Lake Victoria within the western branch of the East African Rift System (EARS) in Tanzania, raised a question as to what extend the region is seismically active. This study examines the geological and geomorphological factors that contributed to the event, emphasizing on structural weaknesses and their link to active tectonic processes. Results show that the NE–SW to NNE–SSW trending faults represent an active extensional regime. A stress tensor model, derived from limited fault slip data, suggests normal faulting with SE-directed extensional forces, closely aligning with the observed mudflow trajectory. Conceptual modeling further reveals how the interplay between weathering, faulting and gravitational forces contributed to slope instability and mass movement. These findings highlight the ongoing neotectonic activity west of Lake Victoria and emphasize on the need to assess geohazard risks in the region. Integrating geological insights into land-use planning and disaster preparedness strategies is called for in order to mitigate future hazards and enhance community resilience.