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Differentiating flow, melt, or fossil seismic anisotropy beneath Ethiopia

Research output: Contribution to journalArticle

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Differentiating flow, melt, or fossil seismic anisotropy beneath Ethiopia. / Hammond, J. O. S.; Kendall, J. -M.; Wookey, J.; Stuart, G. W.; Keir, D.; Ayele, A.

In: Geochemistry, Geophysics, Geosystems, Vol. 15, No. 5, 05.2014, p. 1878-1894.

Research output: Contribution to journalArticle

Harvard

Hammond, JOS, Kendall, J-M, Wookey, J, Stuart, GW, Keir, D & Ayele, A 2014, 'Differentiating flow, melt, or fossil seismic anisotropy beneath Ethiopia', Geochemistry, Geophysics, Geosystems, vol. 15, no. 5, pp. 1878-1894. https://doi.org/10.1002/2013GC005185

APA

Hammond, J. O. S., Kendall, J. -M., Wookey, J., Stuart, G. W., Keir, D., & Ayele, A. (2014). Differentiating flow, melt, or fossil seismic anisotropy beneath Ethiopia. Geochemistry, Geophysics, Geosystems, 15(5), 1878-1894. https://doi.org/10.1002/2013GC005185

Vancouver

Hammond JOS, Kendall J-M, Wookey J, Stuart GW, Keir D, Ayele A. Differentiating flow, melt, or fossil seismic anisotropy beneath Ethiopia. Geochemistry, Geophysics, Geosystems. 2014 May;15(5):1878-1894. https://doi.org/10.1002/2013GC005185

Author

Hammond, J. O. S. ; Kendall, J. -M. ; Wookey, J. ; Stuart, G. W. ; Keir, D. ; Ayele, A. / Differentiating flow, melt, or fossil seismic anisotropy beneath Ethiopia. In: Geochemistry, Geophysics, Geosystems. 2014 ; Vol. 15, No. 5. pp. 1878-1894.

Bibtex

@article{dc9a193cf98e4bbe96dc33bf83eb5a7a,
title = "Differentiating flow, melt, or fossil seismic anisotropy beneath Ethiopia",
abstract = "Ethiopia is a region where continental rifting gives way to oceanic spreading. Yet the role that pre-existing lithospheric structure, melt, mantle flow, or active upwellings may play in this process is debated. Measurements of seismic anisotropy are often used to attempt to understand the contribution that these mechanisms may play. In this study, we use new data in Afar, Ethiopia along with legacy data across Ethiopia, Djibouti, and Yemen to obtain estimates of mantle anisotropy using SKS-wave splitting. We show that two layers of anisotropy exist, and we directly invert for these. We show that fossil anisotropy with fast directions oriented northeast-southwest may be preserved in the lithosphere away from the rift. Beneath the Main Ethiopian Rift and parts of Afar, anisotropy due to shear segregated melt along sharp changes in lithospheric thickness dominates the shear-wave splitting signal in the mantle. Beneath Afar, away from regions with significant lithospheric topography, melt pockets associated with the crustal and uppermost mantle magma storage dominate the signal in localized regions. In general, little anisotropy is seen in the uppermost mantle beneath Afar suggesting melt retains no preferential alignment. These results show the important role melt plays in weakening the lithosphere and imply that as rifting evolves passive upwelling sustains extension. A dominant northeast-southwest anisotropic fast direction is observed in a deeper layer across all of Ethiopia. This suggests that a conduit like plume is lacking beneath Afar today, rather a broad flow from the southwest dominates flow in the upper mantle.",
keywords = "WAVE SPLITTING MEASUREMENTS, EAST-AFRICAN RIFT, UPPER-MANTLE, AFAR DEPRESSION, MIDOCEAN RIDGE, CONTINENTAL BREAKUP, RECEIVER FUNCTIONS, GEOSCOPE STATIONS, SEA-FLOOR, PLUME",
author = "Hammond, {J. O. S.} and Kendall, {J. -M.} and J. Wookey and Stuart, {G. W.} and D. Keir and A. Ayele",
year = "2014",
month = "5",
doi = "10.1002/2013GC005185",
language = "English",
volume = "15",
pages = "1878--1894",
journal = "Geochemistry, Geophysics, Geosystems",
issn = "1525-2027",
publisher = "American Geophysical Union",
number = "5",

}

RIS - suitable for import to EndNote

TY - JOUR

T1 - Differentiating flow, melt, or fossil seismic anisotropy beneath Ethiopia

AU - Hammond, J. O. S.

AU - Kendall, J. -M.

AU - Wookey, J.

AU - Stuart, G. W.

AU - Keir, D.

AU - Ayele, A.

PY - 2014/5

Y1 - 2014/5

N2 - Ethiopia is a region where continental rifting gives way to oceanic spreading. Yet the role that pre-existing lithospheric structure, melt, mantle flow, or active upwellings may play in this process is debated. Measurements of seismic anisotropy are often used to attempt to understand the contribution that these mechanisms may play. In this study, we use new data in Afar, Ethiopia along with legacy data across Ethiopia, Djibouti, and Yemen to obtain estimates of mantle anisotropy using SKS-wave splitting. We show that two layers of anisotropy exist, and we directly invert for these. We show that fossil anisotropy with fast directions oriented northeast-southwest may be preserved in the lithosphere away from the rift. Beneath the Main Ethiopian Rift and parts of Afar, anisotropy due to shear segregated melt along sharp changes in lithospheric thickness dominates the shear-wave splitting signal in the mantle. Beneath Afar, away from regions with significant lithospheric topography, melt pockets associated with the crustal and uppermost mantle magma storage dominate the signal in localized regions. In general, little anisotropy is seen in the uppermost mantle beneath Afar suggesting melt retains no preferential alignment. These results show the important role melt plays in weakening the lithosphere and imply that as rifting evolves passive upwelling sustains extension. A dominant northeast-southwest anisotropic fast direction is observed in a deeper layer across all of Ethiopia. This suggests that a conduit like plume is lacking beneath Afar today, rather a broad flow from the southwest dominates flow in the upper mantle.

AB - Ethiopia is a region where continental rifting gives way to oceanic spreading. Yet the role that pre-existing lithospheric structure, melt, mantle flow, or active upwellings may play in this process is debated. Measurements of seismic anisotropy are often used to attempt to understand the contribution that these mechanisms may play. In this study, we use new data in Afar, Ethiopia along with legacy data across Ethiopia, Djibouti, and Yemen to obtain estimates of mantle anisotropy using SKS-wave splitting. We show that two layers of anisotropy exist, and we directly invert for these. We show that fossil anisotropy with fast directions oriented northeast-southwest may be preserved in the lithosphere away from the rift. Beneath the Main Ethiopian Rift and parts of Afar, anisotropy due to shear segregated melt along sharp changes in lithospheric thickness dominates the shear-wave splitting signal in the mantle. Beneath Afar, away from regions with significant lithospheric topography, melt pockets associated with the crustal and uppermost mantle magma storage dominate the signal in localized regions. In general, little anisotropy is seen in the uppermost mantle beneath Afar suggesting melt retains no preferential alignment. These results show the important role melt plays in weakening the lithosphere and imply that as rifting evolves passive upwelling sustains extension. A dominant northeast-southwest anisotropic fast direction is observed in a deeper layer across all of Ethiopia. This suggests that a conduit like plume is lacking beneath Afar today, rather a broad flow from the southwest dominates flow in the upper mantle.

KW - WAVE SPLITTING MEASUREMENTS

KW - EAST-AFRICAN RIFT

KW - UPPER-MANTLE

KW - AFAR DEPRESSION

KW - MIDOCEAN RIDGE

KW - CONTINENTAL BREAKUP

KW - RECEIVER FUNCTIONS

KW - GEOSCOPE STATIONS

KW - SEA-FLOOR

KW - PLUME

U2 - 10.1002/2013GC005185

DO - 10.1002/2013GC005185

M3 - Article

VL - 15

SP - 1878

EP - 1894

JO - Geochemistry, Geophysics, Geosystems

JF - Geochemistry, Geophysics, Geosystems

SN - 1525-2027

IS - 5

ER -