207-9 Spatial Variation of Strain Rates along Border Faults at the Bifurcating Tip of the Southern Malawi Rift, an Early-Stage Continental Rift

Session: Honoring the Late Professor Mohamed Abdelsalam: Outstanding Researcher, Generous Colleague, Legendary Mentor, and Ambassador for the Geosciences In Africa

Presenting Author:

Authors:

Abstract:

This study analyzes variable strain accommodation within the bifurcating zone of the Malawi Rift. This region is critical for understanding continental rift evolution, as it features the Shire Horst situated between the rift basins and marks both the change in the rift's orientation and its termination zone against the Shire Rift. We apply a multidisciplinary approach that integrates Electrical Resistivity Tomography (ERT), aeromagnetic, and InSAR time-series data to image deformation zones and estimate strain rates. InSAR analysis, spanning 2017 to 2024, reveals ground displacement (uplift and subsidence), interpreted from velocities in the line of sight of the satellite near major border faults. The aeromagnetic data reveals subsurface structures along major faults. The fault throw estimates from the aeromagnetic data, supported by InSAR data, indicates that the Malombe Fault, although considered an intra-rift fault, exhibits almost the same magnitude (about 1.2:1 ratio) of long-term strain accommodation similar to border faults like the Bilila-Mtakataka Fault and the Chirobwe-Ntcheu Fault. We present models that illustrate the conditions and factors driving variations in strain rates along intra-rift faults which include the configuration of the conjugate faults that develop into the rift basin. The variability in strain rates explained by our model of major rift fault initiation and evolution help to identify seismogenic faults and faults with the potential to host high magnitude earthquakes. The findings provide a refined model for the evolution of border faults and intra-rift faults, highlighting their roles in shaping the structural and evolutionary trajectories of rift basins. These results are crucial for re-evaluating geological processes in rift systems and guiding future research and monitoring efforts in tectonically active regions.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.