Bokelmann, G.H.R., Silver, P.G., 2002,
Shear stress at the base of shield lithosphere,
GRL, 29, 2091, doi:10.1029/2002GL015925
One of the basic unresolved issues regarding plate tectonics is the degree
of coupling between surface plates and convecting mantle below. Are the
plates effectively decoupled from the mantle flow field by a low viscosity
asthenosphere, or are they strongly coupled to mantle flow? While these two
views are essentially incompatible, they both do a reasonably good job of
predicting the motions of the surface plates, and cannot therefore be
distinguished on this basis. The significant distinguishing feature for
these models is the magnitude of basal shear stress that is applied to the
base of the plate. While it is difficult to measure this stress directly,
it is possible, in principle, to measure the corresponding deformation of
the plate through observations of seismic anisotropy and to infer stress.
Here we focus on the Canadian Shield, for which we expect strong
plate-mantle interaction. We show that seismic anisotropy can be used to
constrain the magnitude of the stress level applied to the base of the
plate, and to document the level of interaction between tectonic plates and
the mantle below.
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