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Core structure re-examined using new teleseismic data recorded in Antarctica: evidence for, at most, weak cylindrical seismic anisotropy in the inner core

Citation

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]


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The definitive published version is available online at: http://interscience.wiley.com

DOI: doi:10.1111/j.1365-246X.2010.04488.x

Abstract

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.

Item Details

Item Type:Refereed Article
Keywords:composition of the core, body waves, seismic anisitropy, Antarctica
Research Division:Earth Sciences
Research Group:Geophysics
Research Field:Seismology and Seismic Exploration
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Reading, AM (Professor Anya Reading)
ID Code:64619
Year Published:2010
Web of Science® Times Cited:14
Deposited By:Earth Sciences
Deposited On:2010-08-13
Last Modified:2011-04-07
Downloads:0

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