TY - JOUR
T1 - Heterogeneous Strain Distribution in the Malawi (Nyasa) Rift, East Africa
T2 - Implications for Rifting in Magma-Poor, Multi-Segment Rift Systems
AU - Wright, Lachlan J.M.
AU - Scholz, Christopher A.
AU - Muirhead, James D.
AU - Shillington, Donna J.
N1 - Publisher Copyright:
© Wiley Periodicals LLC. The Authors.
PY - 2023/9
Y1 - 2023/9
N2 - Half-graben basins bounded by border faults typify early-stage continental rifts. Deciphering the role that intra-rift faults play in rift basin development is challenging as patterns of early-stage faulting are commonly overprinted by subsequent deformation; yet the characterization of these faults is crucial to understand the fundamental controls on their evolution, their contribution to rift opening, and to assess their seismic hazard. By integrating multiple offshore seismic reflection data sets with age-dated drill core, late-Quaternary and cumulative faulting patterns are characterized in the Central and South Basins of the Malawi (Nyasa) Rift, an active, early-stage rift system. Almost all intra-rift faults offset a late-Quaternary lake lowstand surface, suggesting they are active and should be considered in hazard assessments. Fault throw profiles reveal sawtooth patterns indicating segmented slip histories. Observed extension on intra-rift faults is approximately twice that predicted from hanging wall flexure of the border fault, suggesting that intra-rift faults accommodate a proportion of the regional extension. Cumulative and late-Quaternary throws on intra-rift faults are correlated with throw measured on the border fault in the Central Basin, whereas an anticorrelation is observed in the South Basin. Viewed in a regional context, these differences do not relate solely to the proposed southward younging of the rift. Instead, it is inferred that the distribution of extension is also influenced by variations in lithospheric structure and crustal heterogeneities that are documented along the rift axis.
AB - Half-graben basins bounded by border faults typify early-stage continental rifts. Deciphering the role that intra-rift faults play in rift basin development is challenging as patterns of early-stage faulting are commonly overprinted by subsequent deformation; yet the characterization of these faults is crucial to understand the fundamental controls on their evolution, their contribution to rift opening, and to assess their seismic hazard. By integrating multiple offshore seismic reflection data sets with age-dated drill core, late-Quaternary and cumulative faulting patterns are characterized in the Central and South Basins of the Malawi (Nyasa) Rift, an active, early-stage rift system. Almost all intra-rift faults offset a late-Quaternary lake lowstand surface, suggesting they are active and should be considered in hazard assessments. Fault throw profiles reveal sawtooth patterns indicating segmented slip histories. Observed extension on intra-rift faults is approximately twice that predicted from hanging wall flexure of the border fault, suggesting that intra-rift faults accommodate a proportion of the regional extension. Cumulative and late-Quaternary throws on intra-rift faults are correlated with throw measured on the border fault in the Central Basin, whereas an anticorrelation is observed in the South Basin. Viewed in a regional context, these differences do not relate solely to the proposed southward younging of the rift. Instead, it is inferred that the distribution of extension is also influenced by variations in lithospheric structure and crustal heterogeneities that are documented along the rift axis.
KW - East African Rift
KW - Malawi Rift
KW - extension
KW - normal fault
KW - seismic reflection
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U2 - 10.1029/2022TC007486
DO - 10.1029/2022TC007486
M3 - Article
AN - SCOPUS:85171612129
SN - 0278-7407
VL - 42
JO - Tectonics
JF - Tectonics
IS - 9
M1 - e2022TC007486
ER -