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Apparent Splitting of S Waves Propagating Through an Isotropic Lowermost Mantle
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 [Formula: see text] layer), based on differences in the arrival...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2018
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6049884/ https://www.ncbi.nlm.nih.gov/pubmed/30034981 http://dx.doi.org/10.1002/2017JB014394 |
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author | Parisi, Laura Ferreira, Ana M. G. Ritsema, Jeroen |
author_facet | Parisi, Laura Ferreira, Ana M. G. Ritsema, Jeroen |
author_sort | Parisi, Laura |
collection | PubMed |
description | 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 [Formula: see text] layer), based on differences in the arrival times of vertically (S V) and horizontally (S H) 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 S V and S H 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 s S. For deep earthquakes, apparent splitting can be due to the S wave triplication in D [Formula: see text] , 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. |
format | Online Article Text |
id | pubmed-6049884 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-60498842018-07-20 Apparent Splitting of S Waves Propagating Through an Isotropic Lowermost Mantle Parisi, Laura Ferreira, Ana M. G. Ritsema, Jeroen J Geophys Res Solid Earth Research Articles 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 [Formula: see text] layer), based on differences in the arrival times of vertically (S V) and horizontally (S H) 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 S V and S H 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 s S. For deep earthquakes, apparent splitting can be due to the S wave triplication in D [Formula: see text] , 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. John Wiley and Sons Inc. 2018-05-11 2018-05 /pmc/articles/PMC6049884/ /pubmed/30034981 http://dx.doi.org/10.1002/2017JB014394 Text en ©2018. The Authors. This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Research Articles Parisi, Laura Ferreira, Ana M. G. Ritsema, Jeroen Apparent Splitting of S Waves Propagating Through an Isotropic Lowermost Mantle |
title | Apparent Splitting of S Waves Propagating Through an Isotropic Lowermost Mantle |
title_full | Apparent Splitting of S Waves Propagating Through an Isotropic Lowermost Mantle |
title_fullStr | Apparent Splitting of S Waves Propagating Through an Isotropic Lowermost Mantle |
title_full_unstemmed | Apparent Splitting of S Waves Propagating Through an Isotropic Lowermost Mantle |
title_short | Apparent Splitting of S Waves Propagating Through an Isotropic Lowermost Mantle |
title_sort | apparent splitting of s waves propagating through an isotropic lowermost mantle |
topic | Research Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6049884/ https://www.ncbi.nlm.nih.gov/pubmed/30034981 http://dx.doi.org/10.1002/2017JB014394 |
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