Tectonic model of the Malaŵi rift, Africa

In the seismically active Malaŵi rift (Africa), uplifted segments of the border fault system flank basins with different acoustic stratigraphies, sediment thicknesses and styles of faulting. Regionally curvilinear border fault segments bound sigmoidal-shaped basins linked along the length of the rift in accommodation zones. Accommodation zones that trend oblique to the approximately N-S trend of the rift system occur within the rift valley bounded by border fault segments, suggesting little thinning occurs beneath the elevated rift flanks. Cross-sectional morphologies and fault patterns within Malaŵi rift basins depend on the geometrical arrangement of border fault segments and these patterns are similar to those observed in the Tanganyika rift. Border fault segments locally may reactivate or have an orientation sub-parallel to Proterozoic-Mesozoic structures, but the border fault segmentation and alternating asymmetries of rift basins show no consistent relationship with pre-existing faults and lithologic contacts. The central parts of border fault segments, where maximum vertical displacements have been observed, are separated from any adjacent segment by 50-90 km in both the Malaŵi and Tanganyika rifts. The uniform separation of border fault segments in both the Malaŵi and Tanganyika rifts, despite their differences in age and geologic setting, suggests stress concentrations with an average spatial wavelength of 70 km occur along the length of the Tanganyika and Malaŵi rifts.