Publication 97
Lithospheric anisotropy structure inferred from collocated teleseismic and magnetotelluric
observations: Great Slave Lake shear zone, northern Canada
Eaton, D.W., A.G. Jones and I.J. Ferguson
Abstract
Accurate interpretation of SKS shear-wave splitting
observations requires inherently indeterminate depth
information. Magnetotelluric electrical anisotropies are
depth-constrained, and thereby offer possible resolution of
the SKS conundrum. MT and teleseismic instruments,
deployed across the Great Slave Lake shear zone,
northern Canada, investigated lithospheric anisotropy and
tested a hypothesis that seismic and electrical anisotropy
obliquity can infer mantle strain shear-sense. Lithospheric
mantle MT strike (N60E) differs significantly from
crustal MT strike (N30E). SKS splitting vectors outside
the shear zone exhibit single-layer anisotropy with fast
axis parallel to upper-mantle MT strike and oblique to
present-day plate motion (N135W). Back-azimuth
sensitivity at sites within the 30 km wide shear-zone
imply more complex layering, with two-layer inversion
yielding an upper layer of N20E and a lower layer of
N66E. The MT data help to constrain the depth location
of SKS anisotropy and, taken together, support a model of
fossil lithospheric anisotropy.
Source
Geophysical Research Letters, 31, L19614, doi:10.1029/2004GL020939, 2004.
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Alan G Jones / 25 November 2004 /
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