ACTIVE FAULT MAPPING IN THE NORTHERN BASIN OF THE MALAWI RIFT AND IMPLICATIONS FOR SEISMIC HAZARD.

Chindandali, Patrick Rafiki Nkhondo (2025) ACTIVE FAULT MAPPING IN THE NORTHERN BASIN OF THE MALAWI RIFT AND IMPLICATIONS FOR SEISMIC HAZARD. Masters thesis, Northern Arizona University.

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Abstract

In early-stage rift systems such as the Malawi Rift in the East Africa Rift System, the geometries and slip histories of intrarift faults remain poorly resolved, leaving questions about the partitioning of strain and associated earthquake hazards. Here we focus on the North Basin of the Malawi Rift, a NNW-SSE oriented rift basin bound by the Livingstone border fault; the orientation of this basin is oblique to the regional W-E extension direction, providing the opportunity to examine the influence of obliquity on faulting. During January and February 2024, a geophysical survey was conducted aboard the R/V Timba, acquiring approximately 816 km² of high-resolution multibeam bathymetric data and 1,232 line-kilometers of CHIRP sub-bottom profiles. These datasets reveal a network of active faults within the northern rift basin. The Timba Fault (TF), the largest intra-rift structure, exhibits changes in strike along its length, from NNW-SSE oriented in the north and parallel to the border fault to a more NNW-SSE orientation that is oblique to the border fault in the south. It is at least 44 km long. Other sets of subparallel faults to the TF show scarp heights of lower magnitude. South of the TF, a set of shorter faults with N-S to NNE-SSW strikes that are oblique to the border fault and TF were imaged, providing evidence for strain partitioning associated with oblique rifting. These new oblique faults were not identified in prior mapping studies. A total of nine seismic horizons were interpreted and correlated with age-constrained sedimentary units from drill core Site MAL-2A. We observe that the cumulative scarp height increases with depth, with the oldest horizons (70–100 kyr) displaying the greatest displacement. This pattern indicates that most intrarift faults have been active during that time. Sub-lacustrine channels observed in the northern basin appear to exploit fault-controlled depressions, highlighting the influence of tectonic structure on sediment routing. Estimated moment magnitudes based on fault scaling relationships from Wells and Coppersmith (1994), Leonard (2010), and Wesnousky (2008) suggest that some of the mapped faults in the basin can generate small-to-moderate earthquakes (Mw 4.8–7.0), indicating the seismic hazard potential in the region. These findings provide new constraints on fault architecture, deformation processes, and seismic hazard potential in the northern basin of the Malawi Rift.

Item Type:	Thesis (Masters)
Keywords:	Malawi Rift; East Africa Rift System; Faulting; Slip history; Intrarift faults
Subjects:	Q Science > QE Geology
NAU Depositing Author Academic Status:	Student
Department/Unit:	College of the Environment, Forestry, and Natural Sciences > School of Earth Sciences and Environmental Sustainability
Date Deposited:	07 Aug 2026 18:03
Last Modified:	07 Aug 2026 18:03
URI:	https://openknowledge.nau.edu/id/eprint/6349

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