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ID 25580
file
creator
Hamada, Chiho
Tagawa, Michio
subject
plate-like motion
mantle convection
asymmetric subduction
yield strength
NDC
Earth sciences. Geology
abstract
The dynamical effects of an asymmetric subduction structure on the generation of plate-like motion were investigated using two-dimensional numerical models of the integrated lithosphere-mantle system. To dynamically generate the plate boundary, we introduce a history-dependent rheology in which the yield strength is determined by past fractures. Only the buoyancy due to the internal density contrast consistently drives convective flow, including the motion of the viscous lithosphere, without imposed boundary conditions. We first investigate the effects of plate yield strength, friction at the plate boundary, and plate age on the emergence of plate-like motion with asymmetric subduction. Plate-like motion is generated when maximum plate strength is as high as that estimated by experimental rheology studies. The reason for this is that asymmetric subduction requires a plate-bending force much less than that for symmetric subduction because the plate gently bends when one-sided subduction occurs. In contrast, the strength of the plate boundary has to be very small for emergence of subduction, as several previous studies on the numerical convection and subduction modeling have pointed out. Development of the subducted slab is also controlled by the age of the plate. In the early stages of subduction, older plates increase their velocities faster because of their larger negative buoyancy. After the slab develops, the plate stiffness, that is, both the yield strength and the plate thickness, control plate velocity so that an older plate subducts more sluggishly. We next explore effects of viscosity layering in the underlying mantle, focusing on the mechanism in which the asthenosphere promotes plate motion. The low viscosity under the lithosphere enhances a mantle drag force that drives the plate, not only concentrating the convective flow beneath the plate but also enlarging its aspect ratio. We also examine longevity of the plate-like motion using the convection models with asymmetric subduction. The asymmetrically s
journal title
Physics of the Earth and Planetary Interiors
volume
Volume 166
issue
Issue 3-4
start page
128
end page
146
date of issued
2008-02
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
Copyright (c) 2008 Elsevier B.V.
relation is version of URL
http://dx.doi.org/10.1016/j.pepi.2007.12.004
department
Graduate School of Science