The uppermost mantle seismic velocity and viscosity structure of central West Antarctica
Accurately monitoring and predicting the evolution of the West Antarctic Ice Sheet via secular changes in the Earth's gravity field requires knowledge of the underlying upper mantle viscosity structure. Published seismic models show the West Antarctic lithosphere to be ∼70–100 km thick and unde...
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ftcwashingtonuni:oai:digitalcommons.cwu.edu:cotsfac-1325 2023-05-15T13:47:32+02:00 The uppermost mantle seismic velocity and viscosity structure of central West Antarctica O'Donnell, J. P. Selway, K. Nyblade, A. A. Brazier, R. A. Wiens, D. A. Anandakrishnan, S. Aster, R. C. Huerta, Audrey D. Wilson, T. Winberry, J. Paul 2017-08-15T07:00:00Z application/pdf https://digitalcommons.cwu.edu/cotsfac/325 https://digitalcommons.cwu.edu/cgi/viewcontent.cgi?article=1325&context=cotsfac unknown ScholarWorks@CWU https://digitalcommons.cwu.edu/cotsfac/325 https://digitalcommons.cwu.edu/cgi/viewcontent.cgi?article=1325&context=cotsfac Version of Record: © 2017 Elsevier B.V. All rights reserved. http://creativecommons.org/licenses/by-nc-nd/4.0/ CC-BY-NC-ND All Faculty Scholarship for the College of the Sciences West Antarctica mantle viscosity glacial isostatic adjustment seismic low-velocity zone seismology Geomorphology Geophysics and Seismology Glaciology Tectonics and Structure text 2017 ftcwashingtonuni 2022-10-20T20:29:17Z Accurately monitoring and predicting the evolution of the West Antarctic Ice Sheet via secular changes in the Earth's gravity field requires knowledge of the underlying upper mantle viscosity structure. Published seismic models show the West Antarctic lithosphere to be ∼70–100 km thick and underlain by a low velocity zone extending to at least ∼200 km. Mantle viscosity is dependent on factors including temperature, grain size, the hydrogen content of olivine, the presence of partial melt and applied stress. As seismic wave propagation is particularly sensitive to thermal variations, seismic velocity provides a means of gauging mantle temperature. In 2012, a magnitude 5.6 intraplate earthquake in Marie Byrd Land was recorded on an array of POLENET-ANET seismometers deployed across West Antarctica. We modelled the waveforms recorded by six of the seismic stations in order to determine realistic estimates of temperature and lithology for the lithospheric mantle beneath Marie Byrd Land and the central West Antarctic Rift System. Published mantle xenolith and magnetotelluric data provided constraints on grain size and hydrogen content, respectively, for viscosity modelling. Considering tectonically-plausible stresses, we estimate that the viscosity of the lithospheric mantle beneath Marie Byrd Land and the central West Antarctic Rift System ranges from ∼ 1020 — 1022 Pa s. To extend our analysis to the sublithospheric seismic low velocity zone, we used a published shear wave model. We calculated that the velocity reduction observed between the base of the lithosphere (∼4.4–4.7 km/s) and the centre of the low velocity zone (∼4.2–4.3 km/s) beneath West Antarctica could be caused by a 0.1–0.3% melt fraction or a one order of magnitude reduction in grain size. However, the grain size reduction is inconsistent with our viscosity modelling constraints, suggesting that partial melt more feasibly explains the origin of the low velocity zone. Considering plausible asthenospheric stresses, we estimate the viscosity of the ... Text Antarc* Antarctic Antarctica Ice Sheet Marie Byrd Land West Antarctica Central Washington University: ScholarWorks Anet ENVELOPE(27.987,27.987,65.920,65.920) Antarctic Byrd Marie Byrd Land ENVELOPE(-130.000,-130.000,-78.000,-78.000) West Antarctic Ice Sheet West Antarctica |
institution |
Open Polar |
collection |
Central Washington University: ScholarWorks |
op_collection_id |
ftcwashingtonuni |
language |
unknown |
topic |
West Antarctica mantle viscosity glacial isostatic adjustment seismic low-velocity zone seismology Geomorphology Geophysics and Seismology Glaciology Tectonics and Structure |
spellingShingle |
West Antarctica mantle viscosity glacial isostatic adjustment seismic low-velocity zone seismology Geomorphology Geophysics and Seismology Glaciology Tectonics and Structure O'Donnell, J. P. Selway, K. Nyblade, A. A. Brazier, R. A. Wiens, D. A. Anandakrishnan, S. Aster, R. C. Huerta, Audrey D. Wilson, T. Winberry, J. Paul The uppermost mantle seismic velocity and viscosity structure of central West Antarctica |
topic_facet |
West Antarctica mantle viscosity glacial isostatic adjustment seismic low-velocity zone seismology Geomorphology Geophysics and Seismology Glaciology Tectonics and Structure |
description |
Accurately monitoring and predicting the evolution of the West Antarctic Ice Sheet via secular changes in the Earth's gravity field requires knowledge of the underlying upper mantle viscosity structure. Published seismic models show the West Antarctic lithosphere to be ∼70–100 km thick and underlain by a low velocity zone extending to at least ∼200 km. Mantle viscosity is dependent on factors including temperature, grain size, the hydrogen content of olivine, the presence of partial melt and applied stress. As seismic wave propagation is particularly sensitive to thermal variations, seismic velocity provides a means of gauging mantle temperature. In 2012, a magnitude 5.6 intraplate earthquake in Marie Byrd Land was recorded on an array of POLENET-ANET seismometers deployed across West Antarctica. We modelled the waveforms recorded by six of the seismic stations in order to determine realistic estimates of temperature and lithology for the lithospheric mantle beneath Marie Byrd Land and the central West Antarctic Rift System. Published mantle xenolith and magnetotelluric data provided constraints on grain size and hydrogen content, respectively, for viscosity modelling. Considering tectonically-plausible stresses, we estimate that the viscosity of the lithospheric mantle beneath Marie Byrd Land and the central West Antarctic Rift System ranges from ∼ 1020 — 1022 Pa s. To extend our analysis to the sublithospheric seismic low velocity zone, we used a published shear wave model. We calculated that the velocity reduction observed between the base of the lithosphere (∼4.4–4.7 km/s) and the centre of the low velocity zone (∼4.2–4.3 km/s) beneath West Antarctica could be caused by a 0.1–0.3% melt fraction or a one order of magnitude reduction in grain size. However, the grain size reduction is inconsistent with our viscosity modelling constraints, suggesting that partial melt more feasibly explains the origin of the low velocity zone. Considering plausible asthenospheric stresses, we estimate the viscosity of the ... |
format |
Text |
author |
O'Donnell, J. P. Selway, K. Nyblade, A. A. Brazier, R. A. Wiens, D. A. Anandakrishnan, S. Aster, R. C. Huerta, Audrey D. Wilson, T. Winberry, J. Paul |
author_facet |
O'Donnell, J. P. Selway, K. Nyblade, A. A. Brazier, R. A. Wiens, D. A. Anandakrishnan, S. Aster, R. C. Huerta, Audrey D. Wilson, T. Winberry, J. Paul |
author_sort |
O'Donnell, J. P. |
title |
The uppermost mantle seismic velocity and viscosity structure of central West Antarctica |
title_short |
The uppermost mantle seismic velocity and viscosity structure of central West Antarctica |
title_full |
The uppermost mantle seismic velocity and viscosity structure of central West Antarctica |
title_fullStr |
The uppermost mantle seismic velocity and viscosity structure of central West Antarctica |
title_full_unstemmed |
The uppermost mantle seismic velocity and viscosity structure of central West Antarctica |
title_sort |
uppermost mantle seismic velocity and viscosity structure of central west antarctica |
publisher |
ScholarWorks@CWU |
publishDate |
2017 |
url |
https://digitalcommons.cwu.edu/cotsfac/325 https://digitalcommons.cwu.edu/cgi/viewcontent.cgi?article=1325&context=cotsfac |
long_lat |
ENVELOPE(27.987,27.987,65.920,65.920) ENVELOPE(-130.000,-130.000,-78.000,-78.000) |
geographic |
Anet Antarctic Byrd Marie Byrd Land West Antarctic Ice Sheet West Antarctica |
geographic_facet |
Anet Antarctic Byrd Marie Byrd Land West Antarctic Ice Sheet West Antarctica |
genre |
Antarc* Antarctic Antarctica Ice Sheet Marie Byrd Land West Antarctica |
genre_facet |
Antarc* Antarctic Antarctica Ice Sheet Marie Byrd Land West Antarctica |
op_source |
All Faculty Scholarship for the College of the Sciences |
op_relation |
https://digitalcommons.cwu.edu/cotsfac/325 https://digitalcommons.cwu.edu/cgi/viewcontent.cgi?article=1325&context=cotsfac |
op_rights |
Version of Record: © 2017 Elsevier B.V. All rights reserved. http://creativecommons.org/licenses/by-nc-nd/4.0/ |
op_rightsnorm |
CC-BY-NC-ND |
_version_ |
1766247272894431232 |