Growth of a normal fault system: observations from the Lake Malawi basin of the east African rift

Contreras, Juan; Anders, Mark H.; Scholz, Christopher H.

doi:10.1016/s0191-8141(99)00157-1

Cited by 131 publications

(81 citation statements)

References 19 publications

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“…Existing structures of significance are the Ubendian Proterozoic mobile belt, known to have exerted strong influence on the location and orientation of the northern (Karonga) basin of the Malawi Rift (Rosendahl, 1987;King, 1994), and later Permian Karoo extensional basins onto which many basin separating accommodation zones are juxtaposed (e.g., Versfelt and Rosendahl, 1989) . There are significant occurrences of Karoo sediments in a SW-NE graben to the east of the central basin of the Malawi Rift, and some deposits to the west suggesting this graben continues into the region occupied by Lake Nyasa (Figure 1b The north and central segments have been recognised by previous interpretations (e.g., Ebinger et al, 1987;Scholz, 1989;Soreghan et al, 1999;Contreras et al, 2000), separated by a relay ramp (Chilumba 'platform' Scholz, 1989) that is dissected by normal, preferentially SW-dipping faults (e.g., Soreghan et al, 1999). The south fault segment was first interpreted by Contreras at al., (2000) based upon PROBE data, however, the greater resolution of our data indicates that it does not continue so far north into the basin as they proposed.…”

Section: Nkhata Basin Setting and Architecturementioning

confidence: 60%

“…There are significant occurrences of Karoo sediments in a SW-NE graben to the east of the central basin of the Malawi Rift, and some deposits to the west suggesting this graben continues into the region occupied by Lake Nyasa (Figure 1b The north and central segments have been recognised by previous interpretations (e.g., Ebinger et al, 1987;Scholz, 1989;Soreghan et al, 1999;Contreras et al, 2000), separated by a relay ramp (Chilumba 'platform' Scholz, 1989) that is dissected by normal, preferentially SW-dipping faults (e.g., Soreghan et al, 1999). The south fault segment was first interpreted by Contreras at al., (2000) based upon PROBE data, however, the greater resolution of our data indicates that it does not continue so far north into the basin as they proposed. The central and south fault segment tips, because of limited data, can only be inferred, but overlap by~10 km, and are separated by~6 km.…”

Section: Nkhata Basin Setting and Architecturementioning

confidence: 60%

“…Variation in sediment thickness, generated by subtracting interpolated surfaces, has been used to locate the depocentre for each successive sequence along structures. Depocentre distribution and evolution provide an approximation for the displacement pattern, and thus evolution, of faults (e.g., Schlische and Anders, 1996;McLeod et al, 2000, Contreras et al, 2000Paton, 2006;Mortimer et al, 2007).…”

Section: Data Sets Methodology and Tectono-stratigraphic Frameworkmentioning

confidence: 99%

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Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS)

Mortimer

Paton

Scholz

et al. 2016

Marine and Petroleum Geology

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The Cenozoic East African Rift System (EARS) is an exceptional example of active continental extension, providing opportunities for furthering our understanding of hydrocarbon plays within rifts. It is divided into structurally distinct western and eastern branches. The western branch comprises deep rift basins separated by transfer zones, commonly localised onto pre-existing structures, offering good regional scale hydrocarbon traps. At a basin-scale, local discrete inherited structures might also play an important role on fault localisation and hydrocarbon distribution. Here, we consider the evolution of the Central basin of the Malawi Rift, in particular the influence of pre-existing structural fabrics.Integrating basin-scale multichannel 2D, and high resolution seismic datasets we constrain the border, Mlowe-Nkhata, fault system (MNF) to the west of the basin and smaller Mbamba fault (MF) to the east and document their evolution. Intra basin structures define a series of horsts, which initiated as convergent transfers, along the basin axis. The horsts are offset along a NE-SW striking transfer fault parallel to and along strike of the onshore Karoo 2 (Permo-Triassic) Ruhuhu graben. Discrete pre-existing structures probably determined its location and, oriented obliquely to the extension orientation it accommodated predominantly strike-slip deformation, with more slowly accrued dip-slip.To the north of this transfer fault, the overall basin architecture is asymmetric, thickening to the west throughout; while to the south, an initially symmetric graben architecture became increasingly asymmetric in sediment distribution as strain localised onto the western MNF. The presence of the axial horst increasingly focussed sediment supply to the west. As the transfer fault increased its displacement, so this axial supply was interrupted, effectively starving the south-east while ponding sediments between the western horst margin and the transfer fault. This asymmetric bathymetry and partitioned sedimentation continues to the present-day, overprinting the early basin symmetry and configuration. Sediments deposited earlier become increasingly dissected and fault juxtapositions changed at a small (10-100 m) scale. The observed influence of basin-scale transfer faults on sediment dispersal and fault compartmentalisation due to pre-existing structures oblique to the extension orientation is relevant to analogous exploration settings.

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Section: Nkhata Basin Setting and Architecturementioning

confidence: 60%

Section: Nkhata Basin Setting and Architecturementioning

confidence: 60%

Section: Data Sets Methodology and Tectono-stratigraphic Frameworkmentioning

confidence: 99%

See 1 more Smart Citation

Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS)

Mortimer

Paton

Scholz

et al. 2016

Marine and Petroleum Geology

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“…The most common form of such interactions is when sub-parallel faults overlap, such that the interacting tips lie within the stress shadows of the adjacent fault. The displacement profiles in such cases become asymmetric: the peak slip region is shifted towards the interacting tip and the FTT at that end becomes steeper than that of the distal end [Peacock and Sanderson, 1991;Contreras et al, 2000]. This occurs because the FTT at the interacting tip must overcome both the rupture resistance and the stressdrop of the adjacent fault [Willemse, 1997;Scholz, 2002, pp.…”

Section: Methodsmentioning

confidence: 99%

Slip tapers at the tips of faults and earthquake ruptures

Scholz

Lawler

2004

Geophysical Research Letters

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[1] Slip gradients near the tips of earthquake ruptures and faults are typically linear. For non-interacting faults or earthquake ruptures, tip tapers are scale invariant, and about 1 -2 orders of magnitude larger for faults than for earthquakes. For fault tips interacting with other faults, the taper can be as much as a factor of 10 greater than for non-interacting faults. For earthquake ruptures, taper is also greater by as much as a factor of 10 for tips of rupture segments in the interior of the main rupture, tips in which the earthquake has propagated to the end of the fault, and tips which interact with the stress-drop of a previous earthquake on the same fault. Tip taper for faults increases with the strength of the wall rock. These observations are consistent with fracture mechanics models in which inelastic deformation occurs in a volume surrounding the crack tip.

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“…Significant epistemic uncertainty exists regarding whether a fault ruptures along its entire length in a single event or in a series of smaller earthquakes, affecting the recurrence time interval and magnitude of the seismic events. For instance, the Livingstone and Bilila-Mtakataka faults are considered as a single, continuous structure (Wheeler and Karson, 1989;Jackson and Blenkinsop, 1997), whereas the other five faults consist of segments that could rupture individually (Flannery and Rosendahl, 1990;Contreras et al, 2000). To take into account different rupture possibilities of future earthquakes, the second to fourth models are based on the earthquake rupture of the seven fault systems by considering different rupture hypotheses, i.e., continuous, mixed, and segmented rupture, respectively, in addition to the instrumental catalog-based seismicity.…”

Section: Seismicity and Earthquake Catalog Generationmentioning

confidence: 99%

Seismic Risk Assessment of Urban and Rural Settlements around Lake Malawi

Goda

Gibson

Smith

et al. 2016

Front. Built Environ.

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The seismic risk potential for Malawi is high because traditional adobe and earthen structures are seismically vulnerable and large earthquakes of Mw7.0 or greater may occur in the Malawi Rift. To assess seismic risk of the Malawian communities quantitatively, data and models for exposure, hazard, and vulnerability modules that are suitable for Malawi are integrated. The developed risk model is applied to a retrospective appraisal of the past damaging 2009 Karonga earthquake sequence and to the future earthquake scenarios for long-term risk management purposes. The earthquake impact assessment results highlight that the collapse risk predictions of the Malawian settlements are particularly dependent on the inclusion of large-magnitude earthquakes from the active faults around Lake Malawi and the selection and combination of seismic vulnerability models.

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Growth of a normal fault system: observations from the Lake Malawi basin of the east African rift

Cited by 131 publications

References 19 publications

Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS)

Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS)

Slip tapers at the tips of faults and earthquake ruptures

Seismic Risk Assessment of Urban and Rural Settlements around Lake Malawi

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