Some comments on the effects of lower-mantle anisotropy on SKS and SKKS phases
(2004) In Physics of the Earth and Planetary Interiors 146(3-4). p.469-481- Abstract
- Anisotropy in the lowermost few 100 km of mantle, or D" region, is indicative of deformation-induced alignment of crystals and/or inclusions of material, and as such offers insights into the dynamic nature of this region. Observations of shear-wave splitting in phases that transit this region provide constraints on such anisotropy. We investigate the effects of lower-mantle seismic anisotropy on SKS and SKKS phases through linked effective-medium modelling and ray-based waveform modelling. A mantle with vertical-transverse-isotropy (VTI) will not produce any splitting in such core phases. Instead we consider the effects of azimuthal-anisotropy due to aligned disk-shaped and tubular inclusions and aligned perovskite, peridase and columbite.... (More)
- Anisotropy in the lowermost few 100 km of mantle, or D" region, is indicative of deformation-induced alignment of crystals and/or inclusions of material, and as such offers insights into the dynamic nature of this region. Observations of shear-wave splitting in phases that transit this region provide constraints on such anisotropy. We investigate the effects of lower-mantle seismic anisotropy on SKS and SKKS phases through linked effective-medium modelling and ray-based waveform modelling. A mantle with vertical-transverse-isotropy (VTI) will not produce any splitting in such core phases. Instead we consider the effects of azimuthal-anisotropy due to aligned disk-shaped and tubular inclusions and aligned perovskite, peridase and columbite. Models are constructed subject to constraints imposed by observed anisotropy (<3%) and plausible variations in aggregate isotropic velocities (< +/- 2.5%). Melt-filled inclusions are much more effective in generating anisotropy than solid-filled inclusions and disk-shaped inclusions produce more anisotropy than tubular inclusions. In general the degree of splitting produced by most of the models is small, similar to that produced by the crust (<0.5 s). The exceptions are melt-filled vertically-aligned disk-shaped inclusions and horizontally aligned periclase, the former most likely in low-velocity regions, the latter in high-velocity regions. Both models produce splitting significant enough to mask the effects of upper-mantle anisotropy. Strong azimuthal variations in splitting and discrepancies in SKS and SKKS splitting are diagnostic of these anisotropic models. (C) 2004 Published by Elsevier B.V. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/2441087
- author
- Hall, Stephen LU ; Kendall, J. M. and van der Baan, M.
- publishing date
- 2004
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Physics of the Earth and Planetary Interiors
- volume
- 146
- issue
- 3-4
- pages
- 469 - 481
- publisher
- Elsevier
- external identifiers
-
- scopus:3543062826
- ISSN
- 0031-9201
- DOI
- 10.1016/j.pepi.2004.05.002
- language
- English
- LU publication?
- no
- id
- 88a5e0ab-4772-40c7-a384-c2ef278480ed (old id 2441087)
- date added to LUP
- 2016-04-04 13:50:31
- date last changed
- 2022-02-14 00:23:22
@article{88a5e0ab-4772-40c7-a384-c2ef278480ed,
abstract = {{Anisotropy in the lowermost few 100 km of mantle, or D" region, is indicative of deformation-induced alignment of crystals and/or inclusions of material, and as such offers insights into the dynamic nature of this region. Observations of shear-wave splitting in phases that transit this region provide constraints on such anisotropy. We investigate the effects of lower-mantle seismic anisotropy on SKS and SKKS phases through linked effective-medium modelling and ray-based waveform modelling. A mantle with vertical-transverse-isotropy (VTI) will not produce any splitting in such core phases. Instead we consider the effects of azimuthal-anisotropy due to aligned disk-shaped and tubular inclusions and aligned perovskite, peridase and columbite. Models are constructed subject to constraints imposed by observed anisotropy (<3%) and plausible variations in aggregate isotropic velocities (< +/- 2.5%). Melt-filled inclusions are much more effective in generating anisotropy than solid-filled inclusions and disk-shaped inclusions produce more anisotropy than tubular inclusions. In general the degree of splitting produced by most of the models is small, similar to that produced by the crust (<0.5 s). The exceptions are melt-filled vertically-aligned disk-shaped inclusions and horizontally aligned periclase, the former most likely in low-velocity regions, the latter in high-velocity regions. Both models produce splitting significant enough to mask the effects of upper-mantle anisotropy. Strong azimuthal variations in splitting and discrepancies in SKS and SKKS splitting are diagnostic of these anisotropic models. (C) 2004 Published by Elsevier B.V.}},
author = {{Hall, Stephen and Kendall, J. M. and van der Baan, M.}},
issn = {{0031-9201}},
language = {{eng}},
number = {{3-4}},
pages = {{469--481}},
publisher = {{Elsevier}},
series = {{Physics of the Earth and Planetary Interiors}},
title = {{Some comments on the effects of lower-mantle anisotropy on SKS and SKKS phases}},
url = {{http://dx.doi.org/10.1016/j.pepi.2004.05.002}},
doi = {{10.1016/j.pepi.2004.05.002}},
volume = {{146}},
year = {{2004}},
}