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ID 28631
file
creator
Yoshida, Masaki
subject
mantle convection
numerical calculation
subducting slab
plate margin
viscosity
geoid anomaly
NDC
Earth sciences. Geology
abstract
Instantaneous flow numerical calculations in a three-dimensional spherical shell are employed to investigate the effects of lateral viscosity variations (LVVs) in the lithosphere and mantle on the long-wavelength geoid anomaly. The density anomaly model employed is a combination of seismic tomography and subducting slab models based on seismicity. The global strain-rate model is used to represent weak (low-viscosity) plate margins in the lithosphere. LVVs in the mantle are represented on the basis of the relation between seismic velocity and temperature (i.e., temperature-dependent rheology). When highly viscous slabs in the upper mantle are considered, the observed positive geoid anomaly over subduction zones can be accounted for only when the viscosity contrast between the reference upper mantle and the lower mantle is approximately 103 or lower, and weak plate margins are imposed on the lithosphere. LVVs in the lower mantle exert a large influence on the geoid pattern. The calculated geoid anomalies over subduction zones exhibit generally positive patterns with quite high amplitudes compared with observations, even when the low activation enthalpy of perovskite in the lower mantle is employed. Inferred weak slabs in the lower mantle may be explained in terms of recent mineral physics results, highlighting the possibility of grain-size reduction due to the postspinel phase transition.
journal title
Physics of the Earth and Planetary Interiors
volume
Volume 172
issue
Issue 3-4
start page
278
end page
288
date of issued
2009-02
publisher
Elsevier B.V.
issn
0031-9201
ncid
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
author
rights
(c) 2008 Elsevier B.V. All rights reserved.
relation is version of URL
http://dx.doi.org/10.1016/j.pepi.2008.10.018
department
Graduate School of Science