Seismic evidence for a deeply rooted low-velocity anomaly in the upper mantle beneath the northeastern Afro/Arabian continent

Debayle, E.; Lévêque, Jean Jacques; Cara, Michel

doi:10.1016/s0012-821x(01)00509-x

Cited by 164 publications

(172 citation statements)

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“…To minimize artifacts in our model due to neglecting mode coupling, we restrict our analysis to the fundamental and first four higher Rayleigh modes in the 50-160 s period band. Sensitivity kernels (Debayle et al, 2001) show that using the fundamental and up to the fourth higher mode in this period range achieves good sensitivity over the whole upper mantle. Kennett (1995) also demonstrated that the source contribution is not confined to the immediate neighborhood of the epicenter and the source excitation computation is improved by using a structure specific to the source region.…”

Section: Seismic Constraints On the Upper Mantle Beneath Southern Africamentioning

confidence: 91%

“…We construct the 3D upper mantle model for southern Africa employing the two-step procedure previously used for Australia (Debayle and Kennett, 2000b), eastern Africa (Debayle et al, 2001) and Siberia (Priestley and Debayle, 2003). We first use the automated version (Debayle, 1999) of the Cara and Lévêque (1987) waveform inversion technique to determine a onedimensional (1D) path average upper mantle velocity model compatible with an observed surface wave seismogram.…”

Section: Seismic Constraints On the Upper Mantle Beneath Southern Africamentioning

confidence: 99%

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The state of the upper mantle beneath southern Africa

2006

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Section: Seismic Constraints On the Upper Mantle Beneath Southern Africamentioning

confidence: 91%

Section: Seismic Constraints On the Upper Mantle Beneath Southern Africamentioning

confidence: 99%

The state of the upper mantle beneath southern Africa

2006

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“…In the case of Ethiopia, transition zone thickness, determined by receiver function analysis, shows evidence for thinning compared to the global mean; Cornwell et al (2011) cited this as evidence for high temperatures at transition zone depths, and thus connectivity between shallow low velocities imaged tomographically in Ethiopia (e.g., Bastow et al, 2008;Benoit et al, 2006;Debayle et al, 2001;Hansen et al, 2012;Pasyanos and Nyblade, 2007) and the superplume in the lower mantle beneath.…”

Section: Evidence From Broadband Seismologymentioning

confidence: 99%

The development of extension and magmatism in the Red Sea rift of Afar

et al. 2013

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Despite the importance of continental breakup in plate tectonics, precisely how extensional processes such as brittle faulting, ductile plate stretching, and magma intrusion evolve in space and time during the development of new ocean basins remains poorly understood. The rifting of Arabia from Africa in the Afar depression is an ideal natural laboratory to address this problem since the region exposes subaerially the tectonically active transition from continental rifting to incipient seafloor spreading. We review recent constraints on along-axis variations in rift morphology, crustal and mantle structure, the distribution and style of ongoing faulting, subsurface magmatism and surface volcanism in the Red Sea rift of Afar to understand processes ultimately responsible for the formation of magmatic rifted continental margins. Our synthesis shows that there is a fundamental change in rift morphology from central Afar northward into the Danakil depression, spatially coincident with marked thinning of the crust, an increase in the volume of young basalt flows, and subsidence of the land towards and below sea-level. The variations can be attributed to a northward increase in proportion of extension by ductile plate stretching at the expense of magma intrusion. This is likely in response to a longer history of localised heating and weakening in a narrower rift. Thus, although magma intrusion accommodates strain for a protracted period during rift development, the final stages of breakup are dominated by a phase of plate stretching with a shift from intrusive to extrusive magmatism. This late-stage pulse of decompression melting due to plate thinning may be responsible for the formation of seaward dipping reflector sequences of basalts and sediments, which are ubiquitous at magmatic rifted margins worldwide.

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“…Surface waves as well as regional waveform modeling indicate that on average the Arabian shield crust is 40 -45 km thick, slightly thicker than the average crust for most shields on earth [22][23][24]. Also, slower-than-average P and S velocities were found in the uppermost mantle beneath the western part of the shield [25,26], indicating the upper mantle is anomalously hot and is possibly associated with the uplift of the Arabian shield [26,27]. The low velocity anomaly was found to extend from the Red Sea eastward into the interior of the shield and to be confined to depths shallower than 410 km [26].…”

Section: Introductionmentioning

confidence: 96%

Crustal structure of the Arabian plate: new constraints from the analysis of teleseismic receiver functions

Aldamegh¹,

Sandvol²,

Barazangi³

2005

Earth and Planetary Science Letters

133

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We also employed a grid search waveform modeling technique to estimate the crustal velocity structure for seven stations. A jackknife re-sampling approach was used to estimate errors in the grid search results for three stations. In addition to our results, we have also included published receiver function results from two temporary networks in the Arabian shield and Oman as well as three permanent GSN stations in the region.The average crustal thickness of the late Proterozoic Arabian shield is 39 km. The crust thins to about 23 km along the Red Sea coast and to about 25 km along the margin of the Gulf of Aqaba. In the northern part of the Arabian platform, the crust varies from 33 -37 km thick.However, the crust is thicker (41 -53 km) in the southeastern part of the platform. There is a dramatic change in crustal thickness between the topographic escarpment of the Arabian shield and the shorelines of the Red Sea. We compared our results in the Arabian shield to nine other Proterozoic and Archean shields that include reasonably well-determined Moho depths, mostly based on receiver functions. The average crustal thickness for all shields is 39 km, while the average for Proterozoic shields is 40 km, and the average for Archean shields is 38 km. We found the crustal thickness of Proterozoic shields to vary between 33 and 44 km, while Archean shields vary between 32 and 47 km. Overall, we do not observe a significant difference between Proterozoic and Archean crustal thickness. 3We observed a dramatic change in crustal thickness along the Red Sea margin that occurs over a very short distance. We projected our results over a cross section extending from the Red Sea ridge to the shield escarpment and contrasted it with a typical Atlantic margin. The transition from oceanic to continental crust of the Red Sea margin occurs over a distance of about 250 km, while the transition along a typical portion of the western Atlantic margin occurs at a distance of about 450 km. This important new observation highlights the abruptness of the breakup of Arabia. We argue that a preexisting zone of weakness coupled with anomalously hot upper mantle could have initiated and expedited the breakup.

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Seismic evidence for a deeply rooted low-velocity anomaly in the upper mantle beneath the northeastern Afro/Arabian continent

Cited by 164 publications

References 40 publications

The state of the upper mantle beneath southern Africa

The state of the upper mantle beneath southern Africa

The development of extension and magmatism in the Red Sea rift of Afar

Crustal structure of the Arabian plate: new constraints from the analysis of teleseismic receiver functions

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