The influence of pre-existing structures on the evolution of the southern Kenya Rift Valley — evidence from seismic and gravity studies

Birt, Christopher; Maguire, P. K. H.; Khan, M. Aftab; Thybo, Hans; Keller, G. Randy; Patel, J. P.

doi:10.1016/s0040-1951(97)00105-4

Cited by 108 publications

(136 citation statements)

References 22 publications

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“…These observations are counter to what is observed in magmatic rifts, where lower crustal velocities are higher beneath the rift than outside it owing to extensive magmatic intrusion to the lower and middle crust (e.g. Birt et al 1997;Hamblock et al 2007) or significant crustal thinning, where slow crustal material is replaced by denser, faster velocity upper-mantle material. A reduction in velocities at longer periods would be expected if lithospheric thinning has occurred such that higher velocity lithospheric mantle is replaced by slower, hotter asthenospheric mantle that may contain a small melt fraction.…”

Section: The North and Central Basins Of Lake Malawi: Localization Ofmentioning

confidence: 74%

Surface wave imaging of the weakly extended Malawi Rift from ambient-noise and teleseismic Rayleigh waves from onshore and lake-bottom seismometers

Accardo

Gaherty

Shillington

et al. 2017

Geophysical Journal International

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Section: The North and Central Basins Of Lake Malawi: Localization Ofmentioning

confidence: 74%

Surface wave imaging of the weakly extended Malawi Rift from ambient-noise and teleseismic Rayleigh waves from onshore and lake-bottom seismometers

Accardo

Gaherty

Shillington

et al. 2017

Geophysical Journal International

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“…The sedimentary layer in North Tanzania and South Kenya basins is estimated to be ca. 3.5 km thick (Birt et al 1997;Ebinger et al 1997) and cannot be responsible for such feature. In order to explain the strong negative conversion Px observed (Fig.…”

Section: Intracrustal Interfacesmentioning

confidence: 95%

“…Crustal velocities and thicknesses are well constrained in the Magadi rift zone by the KRISP project refraction line that shows significant crustal variation (ca. 10 km) beneath the central rift valley (Birt et al 1997). Recorded seismicity occurs throughout the region, with relatively deep lower crustal earthquakes beneath the Manyara basin (Albaric et al 2009;Mulibo & Nyblade 2009;Craig et al 2011;Albaric et al 2014), and beneath the Natron basin (Lee et al 2016,Weinstein et al, submitted).…”

Section: G E O L O G I C a L S E T T I N Gmentioning

confidence: 99%

Lithospheric low-velocity zones associated with a magmatic segment of the Tanzanian Rift, East Africa

Plasman¹,

Tiberi

Ebinger

et al. 2017

Geophysical Journal International

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“…MAG and SIN (e.g., Figure 11). A region of low-density, mantle material, which also dips westwards, away from the rift, has been modeled from gravity data along the profile from NYA-CHN [Birt et al, 1997]. On the western flank of the rift the conductivity anomaly may be concomitant with this region of low-density mantle.…”

Section: Is the Deep Crust Conductive?mentioning

confidence: 99%

A three‐dimensional electromagnetic model of the southern Kenya Rift: Departure from two dimensionality as a possible consequence of a rotating stress field

Simpson¹

2000

J. Geophys. Res.

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Abstract. A generic, three-dimensional (3-D) model has been developed which explains the threedimensionality exhibited by magnetovariational (MV) and magnetotelluric (MT) data from southern Kenya. In this model, observed variations in electromagnetic strike with period and location, impedance phase splitting, and peaks in tipper magnitude are all understood in terms of two regionally two-dimensional (2-D) structures striking NW-SE and N-S, respectively. The observed period and location dependence of the electromagnetic strike may arise as an indirect consequence of a rotating stress field, with regional-scale structures formed at different stages of the stress-strain history of Kenya being preserved as conductive lineaments. These conductive structures are not all confined to the upper crust. Thus, whereas stress data provide constraints on rifting at the upper crustal scale, the MT impedance tensor data provide constraints at lithospheric scales. The constraints and resolution provided by the MV and MT data have been rigorously investigated using 3-D forward modeling. Decoupling of the period and site dependence of electromagnetic strike aids resolution and constraint of conductors, rendering attempts to fix an average strike in space and frequency inexpedient. An anomalous apparent "strike" at the center of the Rift Valley reflects neither the N-S strike of the riff, nor the NW-SE striking shear fabric, but is shown to be a virtual strike arising as a result of coupling between the respective strike directions. The NW-SE trending conductivity anomaly straddles the rift and both its flanks, extends to at least middle to lower crustal depths, and appears substantially more electrically anomalous than the rift itself. A hypothesis that melt exists in the mantle directly below the rift at latitude 1.8øS is not supported by the MT data.

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The influence of pre-existing structures on the evolution of the southern Kenya Rift Valley — evidence from seismic and gravity studies

Cited by 108 publications

References 22 publications

Surface wave imaging of the weakly extended Malawi Rift from ambient-noise and teleseismic Rayleigh waves from onshore and lake-bottom seismometers

Surface wave imaging of the weakly extended Malawi Rift from ambient-noise and teleseismic Rayleigh waves from onshore and lake-bottom seismometers

Lithospheric low-velocity zones associated with a magmatic segment of the Tanzanian Rift, East Africa

A three‐dimensional electromagnetic model of the southern Kenya Rift: Departure from two dimensionality as a possible consequence of a rotating stress field

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