Ultrasonic and seismic constraints on crystallographic preferred orientations of the Priestley Glacier shear margin, Antarctica
Crystallographic preferred orientations (CPOs) are particularly important in controlling the mechanical properties of glacial shear margins. Logistical and safety considerations often make direct sampling of shear margins difficult, and geophysical measurements are commonly used to constrain the CPO...
Published in: | The Cryosphere |
---|---|
Main Authors: | , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Copernicus Publications
2022
|
Subjects: | |
Online Access: | https://doi.org/10.5194/tc-16-3313-2022 https://doaj.org/article/cfd0ff3a25934c77a98d217bdba9f415 |
id |
ftdoajarticles:oai:doaj.org/article:cfd0ff3a25934c77a98d217bdba9f415 |
---|---|
record_format |
openpolar |
spelling |
ftdoajarticles:oai:doaj.org/article:cfd0ff3a25934c77a98d217bdba9f415 2023-05-15T13:57:29+02:00 Ultrasonic and seismic constraints on crystallographic preferred orientations of the Priestley Glacier shear margin, Antarctica F. Lutz D. J. Prior H. Still M. H. Bowman B. Boucinhas L. Craw S. Fan D. Kim R. Mulvaney R. E. Thomas C. L. Hulbe 2022-08-01T00:00:00Z https://doi.org/10.5194/tc-16-3313-2022 https://doaj.org/article/cfd0ff3a25934c77a98d217bdba9f415 EN eng Copernicus Publications https://tc.copernicus.org/articles/16/3313/2022/tc-16-3313-2022.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-16-3313-2022 1994-0416 1994-0424 https://doaj.org/article/cfd0ff3a25934c77a98d217bdba9f415 The Cryosphere, Vol 16, Pp 3313-3329 (2022) Environmental sciences GE1-350 Geology QE1-996.5 article 2022 ftdoajarticles https://doi.org/10.5194/tc-16-3313-2022 2022-12-31T01:08:59Z Crystallographic preferred orientations (CPOs) are particularly important in controlling the mechanical properties of glacial shear margins. Logistical and safety considerations often make direct sampling of shear margins difficult, and geophysical measurements are commonly used to constrain the CPOs. We present here the first direct comparison of seismic and ultrasonic data with measured CPOs in a polar shear margin. The measured CPO from ice samples from a 58 m deep borehole in the left lateral shear margin of the Priestley Glacier, Antarctica, is dominated by horizontal c axes aligned sub-perpendicularly to flow. A vertical-seismic-profile experiment with hammer shots up to 50 m away from the borehole, in four different azimuthal directions, shows velocity anisotropy of both P waves and S waves. Matching P-wave data to the anisotropy corresponding to CPO models defined by horizontally aligned c axes gives two possible solutions for the c -axis azimuth, one of which matches the c -axis measurements. If both P-wave and S-wave data are used, there is one best fit for the azimuth and intensity of c -axis alignment that matches the measurements well. Azimuthal P-wave and S-wave ultrasonic data recorded in the laboratory on the ice core show clear anisotropy of P-wave and S-wave velocities in the horizontal plane that match that predicted from the CPO of the samples. With quality data, azimuthal increments of 30 ∘ or less will constrain well the orientation and intensity of c -axis alignment. Our experiments provide a good framework for planning seismic surveys aimed at constraining the anisotropy of shear margins. Article in Journal/Newspaper Antarc* Antarctica ice core Priestley Glacier The Cryosphere Directory of Open Access Journals: DOAJ Articles Priestley ENVELOPE(161.883,161.883,-75.183,-75.183) Priestley Glacier ENVELOPE(163.367,163.367,-74.333,-74.333) The Cryosphere 16 8 3313 3329 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental sciences GE1-350 Geology QE1-996.5 |
spellingShingle |
Environmental sciences GE1-350 Geology QE1-996.5 F. Lutz D. J. Prior H. Still M. H. Bowman B. Boucinhas L. Craw S. Fan D. Kim R. Mulvaney R. E. Thomas C. L. Hulbe Ultrasonic and seismic constraints on crystallographic preferred orientations of the Priestley Glacier shear margin, Antarctica |
topic_facet |
Environmental sciences GE1-350 Geology QE1-996.5 |
description |
Crystallographic preferred orientations (CPOs) are particularly important in controlling the mechanical properties of glacial shear margins. Logistical and safety considerations often make direct sampling of shear margins difficult, and geophysical measurements are commonly used to constrain the CPOs. We present here the first direct comparison of seismic and ultrasonic data with measured CPOs in a polar shear margin. The measured CPO from ice samples from a 58 m deep borehole in the left lateral shear margin of the Priestley Glacier, Antarctica, is dominated by horizontal c axes aligned sub-perpendicularly to flow. A vertical-seismic-profile experiment with hammer shots up to 50 m away from the borehole, in four different azimuthal directions, shows velocity anisotropy of both P waves and S waves. Matching P-wave data to the anisotropy corresponding to CPO models defined by horizontally aligned c axes gives two possible solutions for the c -axis azimuth, one of which matches the c -axis measurements. If both P-wave and S-wave data are used, there is one best fit for the azimuth and intensity of c -axis alignment that matches the measurements well. Azimuthal P-wave and S-wave ultrasonic data recorded in the laboratory on the ice core show clear anisotropy of P-wave and S-wave velocities in the horizontal plane that match that predicted from the CPO of the samples. With quality data, azimuthal increments of 30 ∘ or less will constrain well the orientation and intensity of c -axis alignment. Our experiments provide a good framework for planning seismic surveys aimed at constraining the anisotropy of shear margins. |
format |
Article in Journal/Newspaper |
author |
F. Lutz D. J. Prior H. Still M. H. Bowman B. Boucinhas L. Craw S. Fan D. Kim R. Mulvaney R. E. Thomas C. L. Hulbe |
author_facet |
F. Lutz D. J. Prior H. Still M. H. Bowman B. Boucinhas L. Craw S. Fan D. Kim R. Mulvaney R. E. Thomas C. L. Hulbe |
author_sort |
F. Lutz |
title |
Ultrasonic and seismic constraints on crystallographic preferred orientations of the Priestley Glacier shear margin, Antarctica |
title_short |
Ultrasonic and seismic constraints on crystallographic preferred orientations of the Priestley Glacier shear margin, Antarctica |
title_full |
Ultrasonic and seismic constraints on crystallographic preferred orientations of the Priestley Glacier shear margin, Antarctica |
title_fullStr |
Ultrasonic and seismic constraints on crystallographic preferred orientations of the Priestley Glacier shear margin, Antarctica |
title_full_unstemmed |
Ultrasonic and seismic constraints on crystallographic preferred orientations of the Priestley Glacier shear margin, Antarctica |
title_sort |
ultrasonic and seismic constraints on crystallographic preferred orientations of the priestley glacier shear margin, antarctica |
publisher |
Copernicus Publications |
publishDate |
2022 |
url |
https://doi.org/10.5194/tc-16-3313-2022 https://doaj.org/article/cfd0ff3a25934c77a98d217bdba9f415 |
long_lat |
ENVELOPE(161.883,161.883,-75.183,-75.183) ENVELOPE(163.367,163.367,-74.333,-74.333) |
geographic |
Priestley Priestley Glacier |
geographic_facet |
Priestley Priestley Glacier |
genre |
Antarc* Antarctica ice core Priestley Glacier The Cryosphere |
genre_facet |
Antarc* Antarctica ice core Priestley Glacier The Cryosphere |
op_source |
The Cryosphere, Vol 16, Pp 3313-3329 (2022) |
op_relation |
https://tc.copernicus.org/articles/16/3313/2022/tc-16-3313-2022.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-16-3313-2022 1994-0416 1994-0424 https://doaj.org/article/cfd0ff3a25934c77a98d217bdba9f415 |
op_doi |
https://doi.org/10.5194/tc-16-3313-2022 |
container_title |
The Cryosphere |
container_volume |
16 |
container_issue |
8 |
container_start_page |
3313 |
op_container_end_page |
3329 |
_version_ |
1766265156147347456 |