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


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.


Geophysical Research Letters, 31, L19614, doi:10.1029/2004GL020939, 2004.

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Alan G Jones / 25 November 2004 /