Observations of seismic reflectors in the lower lithosphere beneath the Skagerrak

Lie, J.E.; Pedersen, T. F.; Husebye, E. S.

doi:10.1038/346165a0

Cited by 39 publications

(16 citation statements)

References 9 publications

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“…An important question is then whether such channels also exist beneath continental lithosphere. In this regard, it may be significant that a double seismic reflection, similar to what we have observed, was found by a deep reflection survey at 22 s TWTT beneath the continental shelf of Norway, and has also been tentatively interpreted as the LAB 26 . This raises the intriguing possibility that thin channels of localized partial melt, or volatiles, are widespread features at the base of tectonic plates in general.…”

Section: Letter Researchsupporting

confidence: 63%

“…S g is the crustal refracted S wave. e, Shot gather for shot 11 with band pass filter [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Hz that shows up the R2 reflector with its broad frequency content, and suppresses the low frequency R1 reflection. R sed and P m P represent reflections interpreted to come from the upper surface of the sediment channel on top of the oceanic crust, and from the Moho of the oceanic Pacific plate, respectively.…”

Section: Letter Researchmentioning

confidence: 99%

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A seismic reflection image for the base of a tectonic plate

Stern

Henrys

Okaya

et al. 2015

Nature

117

131

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Plate tectonics successfully describes the surface of Earth as a mosaic of moving lithospheric plates. But it is not clear what happens at the base of the plates, the lithosphere-asthenosphere boundary (LAB). The LAB has been well imaged with converted teleseismic waves, whose 10-40-kilometre wavelength controls the structural resolution. Here we use explosion-generated seismic waves (of about 0.5-kilometre wavelength) to form a high-resolution image for the base of an oceanic plate that is subducting beneath North Island, New Zealand. Our 80-kilometre-wide image is based on P-wave reflections and shows an approximately 15° dipping, abrupt, seismic wave-speed transition (less than 1 kilometre thick) at a depth of about 100 kilometres. The boundary is parallel to the top of the plate and seismic attributes indicate a P-wave speed decrease of at least 8 ± 3 per cent across it. A parallel reflection event approximately 10 kilometres deeper shows that the decrease in P-wave speed is confined to a channel at the base of the plate, which we interpret as a sheared zone of ponded partial melts or volatiles. This is independent, high-resolution evidence for a low-viscosity channel at the LAB that decouples plates from mantle flow beneath, and allows plate tectonics to work.

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Section: Letter Researchsupporting

confidence: 63%

Section: Letter Researchmentioning

confidence: 99%

A seismic reflection image for the base of a tectonic plate

Stern

Henrys

Okaya

et al. 2015

Nature

117

131

View full text Add to dashboard Cite

show abstract

“…Younger orogenic events related to Sveconorwegian (Grenvillian) collision have been recognized by reflection seismic observation of dipping mantle reflections in the North Sea region in Europe (Lie et al, 1990). In two places in northern Europe, spectacular Caledonian structures have been imaged in the upper mantle (Warner et al, 1996;MONA LISA Working Group, 1997).…”

Section: Accepted Manuscriptmentioning

confidence: 97%

Geophysical constraints on geodynamic processes at convergent margins: A global perspective

2016

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“…However, seismic tomography and seismic refraction models would not necessarily indicate the same depth to the base of the lithosphere. In seismic reflection surveys, strong mantle reflectors are often interpreted as the base of the seismic lithosphere, as it is assumed that they originate at the transition from the lithosphere to a zone of partial melt (Lie et al 1990). Furthermore, the base of the seismic lithosphere should be a diffuse boundary if the decrease of the seismic velocities associated with the lithospheric base is caused by high-temperature relaxation or by partial melting (Anderson 1989).…”

Section: Baltic Shieldmentioning

confidence: 99%

“…Distinct, dipping sub-Moho reflections have been identified at 40-110 km depths (BABEL Working Group 1990Lie et al 1990). Dipping at a 15-35 ~ angle, these reflections can be traced laterally over distances of up to 100 km, and in two out of three occurrences they are accompanied by a sharp 5-7 km offset of Moho.…”

Section: Baltic Shieldmentioning

confidence: 99%

Deep Europe today: geophysical synthesis of the upper mantle structure and lithospheric processes over 3.5 Ga

Artemieva

Thybo

Kaban

2006

Memoirs

103

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We present a summary of geophysical models of the subcrustal lithosphere of Europe. This includes the results from seismic (reflection and refraction profiles, P-and S-wave tomography, mantle anisotropy), gravity, thermal, electromagnetic, elastic and petrological studies of the lithospheric mantle. We discuss major tectonic processes as reflected in the lithospheric structure of Europe, from Precambrian terrane accretion and subduction to Phanerozoic rifting, volcanism, subduction and continent-continent collision. The differences in the lithospheric structure of Precambrian and Phanerozoic Europe, as illustrated by a comparative analysis of different geophysical data, are shown to have both a compositional and a thermal origin. We propose an integrated model of physical properties of the European subcrustal lithosphere, with emphasis on the depth intervals around 150 and 250 km. At these depths, seismic velocity models, constrained by body-and surface-wave continent-scale tomography, are compared with mantle temperatures and mantle gravity anomalies. This comparison provides a framework for discussion of the physical or chemical origin of the major lithospheric anomalies and their relation to large-scale tectonic processes, which have formed the present lithosphere of Europe.

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Observations of seismic reflectors in the lower lithosphere beneath the Skagerrak

Cited by 39 publications

References 9 publications

A seismic reflection image for the base of a tectonic plate

A seismic reflection image for the base of a tectonic plate

Geophysical constraints on geodynamic processes at convergent margins: A global perspective

Deep Europe today: geophysical synthesis of the upper mantle structure and lithospheric processes over 3.5 Ga

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