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P-to-S and S-to-P imaging of a sharp lithosphere-asthenosphere boundary beneath eastern North America

P-to-S and S-to-P imaging of a sharp lithosphere-asthenosphere boundary beneath eastern North America
P-to-S and S-to-P imaging of a sharp lithosphere-asthenosphere boundary beneath eastern North America
S-to-P (Sp) scattered energy independently confirms the existence of a seismic velocity discontinuity at the lithosphere-asthenosphere boundary that was previously imaged using P-to-S (Ps) scattered energy in eastern North America. Exploration of the different sensitivities of Ps and Sp scattered energy suggests that the phases contain independent yet complementary high-resolution information regarding velocity contrasts. Combined inversions of Ps and Sp energy have the potential to tightly constrain associated velocity gradients. In eastern North America, inversions of Sp and Ps data require a strong, 5–10% velocity contrast that is also sharp, occurring over less than 11 km at 87–105 km depth. Thermal gradients alone are insufficient to create such a sharp boundary, and therefore another mechanism is required. A boundary in composition, hydration, or a change in anisotropic signature could easily produce a sufficiently localized velocity gradient. Taken separately, the magnitudes of the effects of these mechanisms are too small to match our observed velocity gradients. However, our observations may be explained by a boundary in hydration coupled with a boundary in depletion and/or anisotropy. Alternatively, a small amount of melt in the asthenosphere could explain the velocity gradient. The tight constraints on velocity gradients achieved by combined modeling of Ps and Sp energy offer promise for defining the character of the lithosphere-asthenosphere boundary globally.
0148-0227
B08314
Rychert, Catherine A.
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Rondenay, Stéphane
9e74d655-f55e-4e87-96c9-352cd6439b96
Fischer, Karen M.
5acb751d-c894-4a40-b944-cea48b0ad966
Rychert, Catherine A.
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Rondenay, Stéphane
9e74d655-f55e-4e87-96c9-352cd6439b96
Fischer, Karen M.
5acb751d-c894-4a40-b944-cea48b0ad966

Rychert, Catherine A., Rondenay, Stéphane and Fischer, Karen M. (2007) P-to-S and S-to-P imaging of a sharp lithosphere-asthenosphere boundary beneath eastern North America. Journal of Geophysical Research, 112 (B8), B08314. (doi:10.1029/2006JB004619).

Record type: Article

Abstract

S-to-P (Sp) scattered energy independently confirms the existence of a seismic velocity discontinuity at the lithosphere-asthenosphere boundary that was previously imaged using P-to-S (Ps) scattered energy in eastern North America. Exploration of the different sensitivities of Ps and Sp scattered energy suggests that the phases contain independent yet complementary high-resolution information regarding velocity contrasts. Combined inversions of Ps and Sp energy have the potential to tightly constrain associated velocity gradients. In eastern North America, inversions of Sp and Ps data require a strong, 5–10% velocity contrast that is also sharp, occurring over less than 11 km at 87–105 km depth. Thermal gradients alone are insufficient to create such a sharp boundary, and therefore another mechanism is required. A boundary in composition, hydration, or a change in anisotropic signature could easily produce a sufficiently localized velocity gradient. Taken separately, the magnitudes of the effects of these mechanisms are too small to match our observed velocity gradients. However, our observations may be explained by a boundary in hydration coupled with a boundary in depletion and/or anisotropy. Alternatively, a small amount of melt in the asthenosphere could explain the velocity gradient. The tight constraints on velocity gradients achieved by combined modeling of Ps and Sp energy offer promise for defining the character of the lithosphere-asthenosphere boundary globally.

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Published date: 2007
Organisations: Geology & Geophysics

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Local EPrints ID: 351766
URI: http://eprints.soton.ac.uk/id/eprint/351766
ISSN: 0148-0227
PURE UUID: aee6e270-fc16-47ad-a45c-c799060deb82

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Date deposited: 24 Apr 2013 09:50
Last modified: 14 Mar 2024 13:43

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Contributors

Author: Stéphane Rondenay
Author: Karen M. Fischer

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