MOZART: A Seismological Investigation of the East African Rift in Central Mozambique

Fonseca, J. F.; Chamussa, J.; Domingues, Ana Patrícia; Helffrich, George; Antunes, E.; Aswegen, G. van; Pinto, L. V.; Custódio, Susana; Manhiça, V.

doi:10.1785/0220130082

Cited by 27 publications

(20 citation statements)

References 44 publications

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“…The Cenozoic Era is marked by the formation of incipient rifts resulting from the southward extension of the EARS. Seismically active fault systems point to incipient rifting within the Okavango Rift Zone (ORZ) in northern Botswana (Scholz et al, 1976), and also define the southernmost extension of the Western Branch of the EARS in central Mozambique (Fonseca et al, 2014).…”

Section: Tectonic Backgroundmentioning

confidence: 99%

Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models

White-Gaynor

Nyblade

Durrheim

et al. 2020

Geochem Geophys Geosyst

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We report new P and S wave velocity models of the upper mantle beneath southern Africa using data recorded on seismic stations spanning the entire subcontinent. Beneath most of the Damara Belt, including the Okavango Rift, our models show lower than average velocities (−0.8% Vp; −1.2% Vs) with an abrupt increase in velocities along the terrane's southern margin. We attribute the lower than average velocities to thinner lithosphere (~130 km thick) compared to thicker lithosphere (~200 km thick) immediately to the south under the Kalahari Craton. Beneath the Etendeka Flood Basalt Province, higher than average velocities (0.25% Vp; 0.75% Vs) indicate thicker and/or compositionally distinct lithosphere compared to other parts of the Damara Belt. In the Rehoboth Province, higher than average velocities (0.3% Vp; 0.5% Vs) suggest the presence of a microcraton, as do higher than average velocities (1.0% Vp; 1.5% Vs) under the Southern Irumide Belt. Lower than average velocities (−0.4% Vp; −0.7% Vs) beneath the Bushveld Complex and parts of the Mgondi and Okwa terranes are consistent with previous studies, which attributed them to compositionally modified lithosphere resulting from Precambrian magmatic events. There is little evidence for thermally modified upper mantle beneath any of these terranes which could provide a source of uplift for the Southern African Plateau. In contrast, beneath parts of the Irumide Belt in southern and central Zambia and the Mozambique Belt in central Mozambique, deep-seated low velocity anomalies (−0.7% Vp; −0.8% Vs) can be attributed to upper mantle extensions of the African superplume structure. In the interpretation of our models, we not only reexamine the Precambrian tectonic framework of southern Africa, but also investigate if there is evidence for thermally perturbed upper mantle beneath southern Africa, particularly beneath the uplifted regions of the Southern African Plateau. There has been much discussion (e.g.,

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Section: Tectonic Backgroundmentioning

confidence: 99%

Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models

White-Gaynor

Nyblade

Durrheim

et al. 2020

Geochem Geophys Geosyst

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“…The East African Rift system (EARS) is situated at the plate boundary between the Somalian and Nubian Plates (Chorowicz and Na Bantu Mukonki 1980) and extends over 4,000 km from the triple junction in Afar to fault-controlled basins in Malawi (Ebinger 2005) and south through Mozambique (Fonseca et al 2013). It is the only rift system that is currently active over a continent-wide scale (Yang and Chen 2010).…”

Section: Introductionmentioning

confidence: 99%

Assessing infrequent large earthquakes using geomorphology and geodesy: the Malawi Rift

et al. 2015

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In regions with large, mature fault systems, a characteristic earthquake model may be more appropriate for modelling earthquake occurrence than extrapolating from a short history of small, instrumentally observed earthquakes using the Gutenberg-Richter scaling law. We illustrate how the geomorphology and geodesy of the Malawi Rift, a region with large seismogenic thicknesses, long fault scarps, and slow strain rates, can be used to assess hazard probability levels for large infrequent earthquakes. We estimate potential earthquake size using fault length and recurrence intervals from plate motion velocities and generate a synthetic catalogue of events. Since it is not possible to determine from the geomorphological information if a future rupture will be continuous (7.4 B M W B 8.3 with recurrence intervals of 1,000-4,300 years) or segmented (6.7 B M W B 7.7 with 300-1,900 years), we consider both alternatives separately and also produce a mixed catalogue. We carry out a probabilistic seismic hazard assessment to produce regional-and site-specific hazard estimates. At all return periods and vibration periods, inclusion of fault-derived parameters increases the predicted spectral acceleration above the level predicted from the instrumental catalogue alone, with the most significant changes being in close proximity to the fault systems and the effect being more significant at longer vibration periods. Importantly, the results indicate that standard probabilistic seismic hazard analysis (PSHA) methods using short instrumental records alone tend to underestimate the seismic hazard, especially for the most damaging, extreme magnitude events. For many developing countries in Africa and elsewhere, which are experiencing

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“…Consistent with this, backstripping of the plain's thick sedimentary sequence suggests the underlying lithosphere subsided at rates reminiscent of oceanic lithosphere (Watts, ). However, recent seismological investigations suggest a crustal thickness of about 20 km, which would be unusually thick for oceanic crust (Domingues et al., ; Fonseca et al., ). Deep seismic data would help to confirm whether the Mozambique side of the overlap is underlain by stretched, transitional or oceanic crust with a thick volcanic cover.…”

Section: High‐resolution Kinematic Reconstruction Of the Africa‐indiamentioning

confidence: 99%

New plate kinematic model and tectono‐stratigraphic history of the East African and West Madagascan Margins

2018

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The continental margins of East Africa and West Madagascar are a frontier for hydrocarbon exploration. However, the links between the regional tectonic history of sedimentary basins and margin evolution are relatively poorly understood. We use a plate kinematic model built by joint inversion of seafloor spreading data as a starting point to analyse the evolution of conjugate margin segments and corresponding sedimentary basins. By correlating megasequences in the basins to the plate model we produce a margin‐scale tectono‐stratigraphic framework comprising four phases of tectonic development. During Phase 1 (183–133 Ma) Madagascar/India/Antarctica separated from Africa, first by rifting and later, after breakup (at ca. 170–165 Ma), by seafloor spreading in the West Somali and Mozambique basins and dextral strike‐slip movement on the Davie Fracture Zone. Mixed continental/marine syn‐rift megasequences were deposited in rift basins followed by shallow‐marine early postrift sequences. In Phase 2 (133–89 Ma) spreading ceased in the West Somali basin and Madagascar became fixed to the African plate. However, spreading continued between the African and Antarctic plates and deposition of the early postrift megasequence continued. The onset of spreading on the Mascarene Ridge separated India from Madagascar in Phase 3 (89–60 Ma). Phase 3 was characterized by the onset of deposition of the late postrift megasequence with continued deep marine sedimentation. At the onset of Phase 4 (60 Ma onward) spreading on the Mascarene ridge ceased and the Carlsberg Ridge propagated south to form the Central Indian Ridge, separating India from the Seychelles and the Mascarene Plateau. Late postrift deposition continued until a major unconformity linked to the development of the East African Rift System marked the change to deposition of the modern margin megasequence.

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MOZART: A Seismological Investigation of the East African Rift in Central Mozambique

Cited by 27 publications

References 44 publications

Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models

Lithospheric Boundaries and Upper Mantle Structure Beneath Southern Africa Imaged by P and S Wave Velocity Models

Assessing infrequent large earthquakes using geomorphology and geodesy: the Malawi Rift

New plate kinematic model and tectono‐stratigraphic history of the East African and West Madagascan Margins

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