Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core
We present a significant addition to the data set of traveltimes of seismic PKP waves that sample the Earth's lowermost mantle and core along the Earth's rotation axis. Recorded at permanent Global Seismic Network (GSN) and temporary SSCUA deployment broad-band seismographic stations in An...
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Online Access: | https://doi.org/10.1111/j.1365-246X.2010.04488.x http://ecite.utas.edu.au/64619 |
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ftunivtasecite:oai:ecite.utas.edu.au:64619 2023-05-15T13:35:38+02:00 Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core Leykam, D Tkalcic, H Reading, AM 2010 application/pdf https://doi.org/10.1111/j.1365-246X.2010.04488.x http://ecite.utas.edu.au/64619 en eng Blackwell Publishing Ltd http://ecite.utas.edu.au/64619/1/Leykam, Tkalcic, Reading - Core structure re-examined.pdf http://dx.doi.org/10.1111/j.1365-246X.2010.04488.x Leykam, D and Tkalcic, H and Reading, AM, Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core, Geophysical Journal International, 180, (3) pp. 1329-1343. ISSN 0956-540X (2010) [Refereed Article] http://ecite.utas.edu.au/64619 Earth Sciences Geophysics Seismology and Seismic Exploration Refereed Article PeerReviewed 2010 ftunivtasecite https://doi.org/10.1111/j.1365-246X.2010.04488.x 2019-12-13T21:34:13Z We present a significant addition to the data set of traveltimes of seismic PKP waves that sample the Earth's lowermost mantle and core along the Earth's rotation axis. Recorded at permanent Global Seismic Network (GSN) and temporary SSCUA deployment broad-band seismographic stations in Antarctica, the new data improve the previously poor and biased coverage that underlies the seismic constraints on recent models of inner core structure and anisotropy. On the one hand, new differential PKP traveltime measurements improve the sampling of predominantly the eastern inner core hemisphere. PKPab-df and PKPbc-df differential traveltime residuals, with respect to the spherically symmetric model ak135, are consistently smaller than two seconds along the northsouth paths sampled. Axially symmetric models of inner core seismic anisotropy with fast axis parallel to the Earth's rotation axis require a weak anisotropy of (0.7 0.1) per cent to be consistent with our PKPbc-df observations. PKPbc-df residuals from the quasi-eastern hemisphere indicate (0.4 0.1) per cent anisotropy. If only PKPbc-df observations from the top 200 km of this hemisphere are considered, this is reduced to (0.1 0.2) per cent, consistent with an isotropic layer. On the other hand, new absolute PKP traveltime measurements add to the sampling of both hemispheres of the inner core, but it is difficult to use them with more confidence to assess structure of the core since they are affected by crustal and mantle structure and source uncertainties. The newly collected data set also increases constraints on D" structure beneath the South Pole. In contrast to previous inferences based on data from northern stations, we find no evidence of a velocity heterogeneity in the outer core near the inner core boundary associated with the cylinder tangent to the inner core in the southern hemisphere. Article in Journal/Newspaper Antarc* Antarctica South pole South pole eCite UTAS (University of Tasmania) South Pole Geophysical Journal International 180 3 1329 1343 |
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Open Polar |
collection |
eCite UTAS (University of Tasmania) |
op_collection_id |
ftunivtasecite |
language |
English |
topic |
Earth Sciences Geophysics Seismology and Seismic Exploration |
spellingShingle |
Earth Sciences Geophysics Seismology and Seismic Exploration Leykam, D Tkalcic, H Reading, AM Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core |
topic_facet |
Earth Sciences Geophysics Seismology and Seismic Exploration |
description |
We present a significant addition to the data set of traveltimes of seismic PKP waves that sample the Earth's lowermost mantle and core along the Earth's rotation axis. Recorded at permanent Global Seismic Network (GSN) and temporary SSCUA deployment broad-band seismographic stations in Antarctica, the new data improve the previously poor and biased coverage that underlies the seismic constraints on recent models of inner core structure and anisotropy. On the one hand, new differential PKP traveltime measurements improve the sampling of predominantly the eastern inner core hemisphere. PKPab-df and PKPbc-df differential traveltime residuals, with respect to the spherically symmetric model ak135, are consistently smaller than two seconds along the northsouth paths sampled. Axially symmetric models of inner core seismic anisotropy with fast axis parallel to the Earth's rotation axis require a weak anisotropy of (0.7 0.1) per cent to be consistent with our PKPbc-df observations. PKPbc-df residuals from the quasi-eastern hemisphere indicate (0.4 0.1) per cent anisotropy. If only PKPbc-df observations from the top 200 km of this hemisphere are considered, this is reduced to (0.1 0.2) per cent, consistent with an isotropic layer. On the other hand, new absolute PKP traveltime measurements add to the sampling of both hemispheres of the inner core, but it is difficult to use them with more confidence to assess structure of the core since they are affected by crustal and mantle structure and source uncertainties. The newly collected data set also increases constraints on D" structure beneath the South Pole. In contrast to previous inferences based on data from northern stations, we find no evidence of a velocity heterogeneity in the outer core near the inner core boundary associated with the cylinder tangent to the inner core in the southern hemisphere. |
format |
Article in Journal/Newspaper |
author |
Leykam, D Tkalcic, H Reading, AM |
author_facet |
Leykam, D Tkalcic, H Reading, AM |
author_sort |
Leykam, D |
title |
Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core |
title_short |
Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core |
title_full |
Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core |
title_fullStr |
Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core |
title_full_unstemmed |
Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core |
title_sort |
core structure re-examined using new teleseismic data recorded in antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core |
publisher |
Blackwell Publishing Ltd |
publishDate |
2010 |
url |
https://doi.org/10.1111/j.1365-246X.2010.04488.x http://ecite.utas.edu.au/64619 |
geographic |
South Pole |
geographic_facet |
South Pole |
genre |
Antarc* Antarctica South pole South pole |
genre_facet |
Antarc* Antarctica South pole South pole |
op_relation |
http://ecite.utas.edu.au/64619/1/Leykam, Tkalcic, Reading - Core structure re-examined.pdf http://dx.doi.org/10.1111/j.1365-246X.2010.04488.x Leykam, D and Tkalcic, H and Reading, AM, Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core, Geophysical Journal International, 180, (3) pp. 1329-1343. ISSN 0956-540X (2010) [Refereed Article] http://ecite.utas.edu.au/64619 |
op_doi |
https://doi.org/10.1111/j.1365-246X.2010.04488.x |
container_title |
Geophysical Journal International |
container_volume |
180 |
container_issue |
3 |
container_start_page |
1329 |
op_container_end_page |
1343 |
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1766068285041803264 |