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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ftanucanberra:oai:openresearch-repository.anu.edu.au:1885/31811 2024-01-14T10:01:21+01:00 Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core Leykam, Daniel Tkalčić, Hrvoje Reading, Anya M. http://hdl.handle.net/1885/31811 https://doi.org/10.1111/j.1365-246X.2010.04488.x https://openresearch-repository.anu.edu.au/bitstream/1885/31811/7/01_Leykam_Core_structure_re-examined_2010.pdf.jpg unknown Blackwell Publishing Ltd 0956-540X http://hdl.handle.net/1885/31811 doi:10.1111/j.1365-246X.2010.04488.x https://openresearch-repository.anu.edu.au/bitstream/1885/31811/7/01_Leykam_Core_structure_re-examined_2010.pdf.jpg Geophysical Journal International Keywords: body wave crustal structure inner core mantle structure seismic anisotropy seismic data teleseismic wave travel time Antarctica Antarctica Body waves Composition of the core Journal article ftanucanberra https://doi.org/10.1111/j.1365-246X.2010.04488.x 2023-12-15T09:37:04Z 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 north-south 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 Australian National University: ANU Digital Collections South Pole Geophysical Journal International 180 3 1329 1343 |
institution |
Open Polar |
collection |
Australian National University: ANU Digital Collections |
op_collection_id |
ftanucanberra |
language |
unknown |
topic |
Keywords: body wave crustal structure inner core mantle structure seismic anisotropy seismic data teleseismic wave travel time Antarctica Antarctica Body waves Composition of the core |
spellingShingle |
Keywords: body wave crustal structure inner core mantle structure seismic anisotropy seismic data teleseismic wave travel time Antarctica Antarctica Body waves Composition of the core Leykam, Daniel Tkalčić, Hrvoje Reading, Anya M. 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 |
Keywords: body wave crustal structure inner core mantle structure seismic anisotropy seismic data teleseismic wave travel time Antarctica Antarctica Body waves Composition of the core |
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 north-south 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, Daniel Tkalčić, Hrvoje Reading, Anya M. |
author_facet |
Leykam, Daniel Tkalčić, Hrvoje Reading, Anya M. |
author_sort |
Leykam, Daniel |
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 |
url |
http://hdl.handle.net/1885/31811 https://doi.org/10.1111/j.1365-246X.2010.04488.x https://openresearch-repository.anu.edu.au/bitstream/1885/31811/7/01_Leykam_Core_structure_re-examined_2010.pdf.jpg |
geographic |
South Pole |
geographic_facet |
South Pole |
genre |
Antarc* Antarctica South pole South pole |
genre_facet |
Antarc* Antarctica South pole South pole |
op_source |
Geophysical Journal International |
op_relation |
0956-540X http://hdl.handle.net/1885/31811 doi:10.1111/j.1365-246X.2010.04488.x https://openresearch-repository.anu.edu.au/bitstream/1885/31811/7/01_Leykam_Core_structure_re-examined_2010.pdf.jpg |
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 |
_version_ |
1788067141350588416 |