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Seismic evidence for accumulated oceanic crust above the

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Plate tectonics - Seismic tomography | Britannica.c

Plate tectonics - Plate tectonics - Seismic tomography: A powerful technique, seismic tomography, provides insight into the understanding of plate-driving mechanisms. This technique is similar in principle to that of the CT (computed tomography) scan and creates three-dimensional images of Earth’s interior by combining information from many earthquakes.

Seismic evidence for accumulated oceanic crust above the .

[1] High‐pressure assemblages of subducted oceanic crust are denser than the normal upper mantle but less dense than the uppermost lower mantle. Thus subducted oceanic crust may accumulate at the base of the upper mantle. Direct observational evidence for this hypothesis, however, remains elusive.

(PDF) Seismic evidence for broken oceanic crust in the .

The seismic data reveal that the subducting crust and oceanic Moho-the crust-mantle boundary-are broken and displaced by landward-dipping thrust ramps, suggesting that the megathrust now lies in ...

Plate tectonics - Seismic tomography | Britannica.c

Plate tectonics - Plate tectonics - Seismic tomography: A powerful technique, seismic tomography, provides insight into the understanding of plate-driving mechanisms. This technique is similar in principle to that of the CT (computed tomography) scan and creates three-dimensional images of Earth’s interior by combining information from many earthquakes.

Seismic evidence for accumulated oceanic crust above the 660-km discontinuity beneath southern Afri

Thus subducted oceanic crust may accumulate at the base of the upper mantle. Direct observational evidence for this hypothesis, however, remains elusive. We present an analysis of a negative-polarity shear wave converted from compressional wave at a seismic discontinuity near 570 - 600 km depth beneath southern Africa.

1. What is the evidence for continental drift and plate .

Theories of continental drift and plate tectonics including: -The basic structure of the earth including the lithosphere, asthenosphere and the role of convection currents -Evidence for sea-floor spreading; paleomagnetism; the age of sea floor rocks -evidence from ancient glaciations -Fossil records… Learn with flashcards, games, and more — for free.

Seismic images of the megathrust rupture during the 25th .

Since it would be difficult to propagate the megathrust rupture above the saw-toothed oceanic crust, the megathrust rupture might lie in the oceanic crust or in the oceanic mantle [Singh et al., 2008]. The presence of the re-activated thrusts and complex oceanic crust interface in Figures 3 and 4 support this hypothesis.

Seismic evidence for accumulated oceanic crust above the .

Seismic evidence for accumulated oceanic crust above the 660-km discontinuity beneath southern Africa Article (PDF Available) in Geophysical Research Letters 30:1925 · September 2003 with 32 Reads

Seismic evidence for accumulated oceanic crust above the .

Thus subducted oceanic crust may accumulate at the base of the upper mantle. Direct observational evidence for this hypothesis, however, remains elusive. We present an analysis of a negative-polarity shear wave converted from compressional wave at a seismic discontinuity near 570-600 km depth beneath southern Africa.

Seismic evidence for accumulated oceanic crust above the .

Thus subducted oceanic crust may accumulate at the base ... Seismic evidence for accumulated oceanic crust above the 660‐km discontinuity beneath southern Africa - Shen - 2003 - Geophysical Research Letters - Wiley Online Library

A new conceptual model for whole mantle convection and the .

A new conceptual model for whole mantle convection and the origin of hotspot plumes. ... provided seismic evidence for a low seismic velocity zone that could account for accumulated oceanic crust above the 660-km seismic discontinuity beneath the southern African craton. It is presumed that this accumulation of crustal material developed during ...

Seismic evidence for accumulated oceanic crust above the .

Seismic evidence for accumulated oceanic crust above the 660-km discontinuity beneath southern Africa Yang Shen University of Rhode Island, Graduate School of Oceanography, Narragansett, Rhode Island, USA

Seismic Evidence for Accumulated Oceanic Crust Above the .

Seismic Evidence for Accumulated Oceanic Crust Above the 660-km Discontinuity Beneath Southern Africa - fig. 1 Figure 1. (a) Locations of broadband seismic stations (triangles) and the profile of the receiver function stacks (line).

Seismic evidence for overpressured subducted oceanic crust .

Seismic evidence for overpressured subducted oceanic crust and megathrust fault sealing ... where a serpentinite layer is interpreted to form above subducting oceanic crust at onset of ...

Thermal, hydrous, and mechanical states of the mantle .

Observations of P-to-S conversions from the seismic discontinuities near 410 and 660 km depth reveal the shoaling of the 410-km discontinuity and the deepening of the 660-km discontinuity beneath the Archaean cratons in southern Africa; consequently, the mantle transition zone is 20 km thicker than beneath post-Archaean regions and the global average.

Seismic Evidence for Accumulated Oceanic Crust Above the .

Seismic Evidence for Accumulated Oceanic Crust Above the 660-km Discontinuity Beneath Southern Africa - fig. 2 Figure 2. (a) Two possible scenarios may cause a negative-polarity P-to-S conversion near a 590-km depth: a uniform reduction in velocity at the base of the upper mantle (dashed line) and a velocity reduction near 590 km followed by a greater than normal velocity gradient (dotted line).

35. Interpretation of Seismic-Reflection Data of the .

The geological and geophysical evidence that we have assembled as well as other published data suggest that one or more landward-dipping slabs of ocean crust underlie the upper continental slope structurally above an extension of oceanic crust landward from the Trench axis.

Oceanic crust in the mid-mantle beneath west-central .

To understand if the oceanic crust observed in the mid-mantle has separated from or attached to the main subducting lithosphere, a 77 km thick whole slab model is constructed for simulation for the 2010 March 20 event (Fig. S7, Supporting Information). A structure of 70 km thick lithosphere underlying 7 km thick oceanic crust is placed below ...

Seismic evidence for accumulated oceanic crust above the 660-km discontinuity beneath southern Afri

SEISMIC EVIDENCE FOR ACCUMULATED OCEANIC CRUST ABOVE THE 660-KM DISCONTINUITY BENEATH SOUTHERN AFRICA Yang Shen • University of Rhode Island John Blum • University of California, San Diego High-pressure assemblages of subducted oceanic crust are denser than the normal upper mantle but less dense than the

(PDF) Seismic structure of oceanic crust in the western .

We examine the seismic structure of Cretaceous-aged ocean crust north of the Blake Spur fracture zone in the western North Atlantic by using a combination of multichannel seismic and wide-angle reflection/refraction data. Although the oceanic crust