Upper mantle seismic anisotropy beneath the West Antarctic Rift System and surrounding region from shear wave splitting analysis
We constrain azimuthal anisotropy in the West Antarctic upper mantle using shear wave splitting parameters obtained from teleseismic SKS, SKKS and PKS phases recorded at 37 broad-band seismometres deployed by the POLENET/ANET project. We use an eigenvalue technique to linearize the rotated and shift...
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fthighwire:oai:open-archive.highwire.org:gji:198/1/414 2023-05-15T13:24:16+02:00 Upper mantle seismic anisotropy beneath the West Antarctic Rift System and surrounding region from shear wave splitting analysis Accardo, Natalie J. Wiens, Douglas A. Hernandez, Stephen Aster, Richard C. Nyblade, Andrew Huerta, Audrey Anandakrishnan, Sridhar Wilson, Terry Heeszel, David S. Dalziel, Ian W. D. 2014-06-19 04:25:28.0 text/html http://gji.oxfordjournals.org/cgi/content/short/198/1/414 https://doi.org/10.1093/gji/ggu117 en eng Oxford University Press http://gji.oxfordjournals.org/cgi/content/short/198/1/414 http://dx.doi.org/10.1093/gji/ggu117 Copyright (C) 2014, Oxford University Press Seismology TEXT 2014 fthighwire https://doi.org/10.1093/gji/ggu117 2016-11-16T17:03:45Z We constrain azimuthal anisotropy in the West Antarctic upper mantle using shear wave splitting parameters obtained from teleseismic SKS, SKKS and PKS phases recorded at 37 broad-band seismometres deployed by the POLENET/ANET project. We use an eigenvalue technique to linearize the rotated and shifted shear wave horizontal particle motions and determine the fast direction and delay time for each arrival. High-quality measurements are stacked to determine the best fitting splitting parameters for each station. Overall, fast anisotropic directions are oriented at large angles to the direction of Antarctic absolute plate motion in both hotspot and no-net-rotation frameworks, showing that the anisotropy does not result from shear due to plate motion over the mantle. Further, the West Antarctic directions are substantially different from those of East Antarctica, indicating that anisotropy across the continent reflects multiple mantle regimes. We suggest that the observed anisotropy along the central Transantarctic Mountains (TAM) and adjacent West Antarctic Rift System (WARS), one of the largest zones of extended continental crust on Earth, results from asthenospheric mantle strain associated with the final pulse of western WARS extension in the late Miocene. Strong and consistent anisotropy throughout the WARS indicate fast axes subparallel to the inferred extension direction, a result unlike reports from the East African rift system and rifts within the Basin and Range, which show much greater variation. We contend that ductile shearing rather than magmatic intrusion may have been the controlling mechanism for accumulation and retention of such coherent, widespread anisotropic fabric. Splitting beneath the Marie Byrd Land Dome (MBL) is weaker than that observed elsewhere within the WARS, but shows a consistent fast direction, possibly representative of anisotropy that has been ‘frozen-in’ to remnant thicker lithosphere. Fast directions observed inland from the Amundsen Sea appear to be radial to the dome and may ... Text Amundsen Sea Antarc* Antarctic Antarctica East Antarctica Marie Byrd Land HighWire Press (Stanford University) Amundsen Sea Anet ENVELOPE(27.987,27.987,65.920,65.920) Antarctic Byrd East Antarctica Marie Byrd Land ENVELOPE(-130.000,-130.000,-78.000,-78.000) Transantarctic Mountains Geophysical Journal International 198 1 414 429 |
institution |
Open Polar |
collection |
HighWire Press (Stanford University) |
op_collection_id |
fthighwire |
language |
English |
topic |
Seismology |
spellingShingle |
Seismology Accardo, Natalie J. Wiens, Douglas A. Hernandez, Stephen Aster, Richard C. Nyblade, Andrew Huerta, Audrey Anandakrishnan, Sridhar Wilson, Terry Heeszel, David S. Dalziel, Ian W. D. Upper mantle seismic anisotropy beneath the West Antarctic Rift System and surrounding region from shear wave splitting analysis |
topic_facet |
Seismology |
description |
We constrain azimuthal anisotropy in the West Antarctic upper mantle using shear wave splitting parameters obtained from teleseismic SKS, SKKS and PKS phases recorded at 37 broad-band seismometres deployed by the POLENET/ANET project. We use an eigenvalue technique to linearize the rotated and shifted shear wave horizontal particle motions and determine the fast direction and delay time for each arrival. High-quality measurements are stacked to determine the best fitting splitting parameters for each station. Overall, fast anisotropic directions are oriented at large angles to the direction of Antarctic absolute plate motion in both hotspot and no-net-rotation frameworks, showing that the anisotropy does not result from shear due to plate motion over the mantle. Further, the West Antarctic directions are substantially different from those of East Antarctica, indicating that anisotropy across the continent reflects multiple mantle regimes. We suggest that the observed anisotropy along the central Transantarctic Mountains (TAM) and adjacent West Antarctic Rift System (WARS), one of the largest zones of extended continental crust on Earth, results from asthenospheric mantle strain associated with the final pulse of western WARS extension in the late Miocene. Strong and consistent anisotropy throughout the WARS indicate fast axes subparallel to the inferred extension direction, a result unlike reports from the East African rift system and rifts within the Basin and Range, which show much greater variation. We contend that ductile shearing rather than magmatic intrusion may have been the controlling mechanism for accumulation and retention of such coherent, widespread anisotropic fabric. Splitting beneath the Marie Byrd Land Dome (MBL) is weaker than that observed elsewhere within the WARS, but shows a consistent fast direction, possibly representative of anisotropy that has been ‘frozen-in’ to remnant thicker lithosphere. Fast directions observed inland from the Amundsen Sea appear to be radial to the dome and may ... |
format |
Text |
author |
Accardo, Natalie J. Wiens, Douglas A. Hernandez, Stephen Aster, Richard C. Nyblade, Andrew Huerta, Audrey Anandakrishnan, Sridhar Wilson, Terry Heeszel, David S. Dalziel, Ian W. D. |
author_facet |
Accardo, Natalie J. Wiens, Douglas A. Hernandez, Stephen Aster, Richard C. Nyblade, Andrew Huerta, Audrey Anandakrishnan, Sridhar Wilson, Terry Heeszel, David S. Dalziel, Ian W. D. |
author_sort |
Accardo, Natalie J. |
title |
Upper mantle seismic anisotropy beneath the West Antarctic Rift System and surrounding region from shear wave splitting analysis |
title_short |
Upper mantle seismic anisotropy beneath the West Antarctic Rift System and surrounding region from shear wave splitting analysis |
title_full |
Upper mantle seismic anisotropy beneath the West Antarctic Rift System and surrounding region from shear wave splitting analysis |
title_fullStr |
Upper mantle seismic anisotropy beneath the West Antarctic Rift System and surrounding region from shear wave splitting analysis |
title_full_unstemmed |
Upper mantle seismic anisotropy beneath the West Antarctic Rift System and surrounding region from shear wave splitting analysis |
title_sort |
upper mantle seismic anisotropy beneath the west antarctic rift system and surrounding region from shear wave splitting analysis |
publisher |
Oxford University Press |
publishDate |
2014 |
url |
http://gji.oxfordjournals.org/cgi/content/short/198/1/414 https://doi.org/10.1093/gji/ggu117 |
long_lat |
ENVELOPE(27.987,27.987,65.920,65.920) ENVELOPE(-130.000,-130.000,-78.000,-78.000) |
geographic |
Amundsen Sea Anet Antarctic Byrd East Antarctica Marie Byrd Land Transantarctic Mountains |
geographic_facet |
Amundsen Sea Anet Antarctic Byrd East Antarctica Marie Byrd Land Transantarctic Mountains |
genre |
Amundsen Sea Antarc* Antarctic Antarctica East Antarctica Marie Byrd Land |
genre_facet |
Amundsen Sea Antarc* Antarctic Antarctica East Antarctica Marie Byrd Land |
op_relation |
http://gji.oxfordjournals.org/cgi/content/short/198/1/414 http://dx.doi.org/10.1093/gji/ggu117 |
op_rights |
Copyright (C) 2014, Oxford University Press |
op_doi |
https://doi.org/10.1093/gji/ggu117 |
container_title |
Geophysical Journal International |
container_volume |
198 |
container_issue |
1 |
container_start_page |
414 |
op_container_end_page |
429 |
_version_ |
1766378409966960640 |