Parisi, L;
Ferreira, AMG;
Ritsema, J;
(2018)
Apparent Splitting of S Waves Propagating Through an Isotropic Lowermost Mantle.
Journal of Geophysical Research
, 123
(5)
pp. 3909-3922.
10.1002/2017JB014394.
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Abstract
Observations of shear wave anisotropy are key for understanding the mineralogical structure and flow in the mantle. Several researchers have reported the presence of seismic anisotropy in the lowermost 150–250 km of the mantle (i.e., D urn:x-wiley:jgrb:media:jgrb52636:jgrb52636-math-0002 layer), based on differences in the arrival times of vertically (SV) and horizontally (SH) polarized shear waves. By computing waveforms at a period > 6 s for a wide range of 1‐D and 3‐D Earth structures, we illustrate that a time shift (i.e., apparent splitting) between SV and SH may appear in purely isotropic simulations. This may be misinterpreted as shear wave anisotropy. For near‐surface earthquakes, apparent shear wave splitting can result from the interference of S with the surface reflection sS. For deep earthquakes, apparent splitting can be due to the S wave triplication in D urn:x-wiley:jgrb:media:jgrb52636:jgrb52636-math-0003, reflections off discontinuities in the upper mantle, and 3‐D heterogeneity. The wave effects due to anomalous isotropic structure may not be easily distinguished from purely anisotropic effects if the analysis does not involve full waveform simulations.
| Type: | Article |
|---|---|
| Title: | Apparent Splitting of S Waves Propagating Through an Isotropic Lowermost Mantle |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1002/2017JB014394 |
| Publisher version: | https://doi.org/10.1002/2017JB014394 |
| Language: | English |
| Additional information: | This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. See: https://creativecommons.org/licenses/by-nc-nd/4.0/ |
| Keywords: | Shear wave splitting, D'layer mantle anisotropy, core‐mantle boundary, lowermost mantle |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10048271 |
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