Lithospheric anisotropy structure inferred from collocated teleseismic and magnetotelluric observations: Great Slave Lake shear zone, northern Canada

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 (N60°E) differs significantly from crustal MT strike (N30°E). 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 (N135°W). 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 ∼N20°E and a lower layer of ∼N66°E. The MT data help to constrain the depth location of SKS anisotropy and, taken together, support a model of fossil lithospheric anisotropy.