Seismic anisotropy of the Canadian High Arctic: evidence from shear-wave splitting

The Canadian High Arctic preserves a long and complex tectonic history, including craton formation, multiple periods of orogenesis, extension and basin formation, and the development of a passive continental margin. We investigate the possible preservation of deformational structures throughout the High Arctic subcontinental lithosphere using measurements of seismic anisotropy from shear wave splitting at 11 seismograph stations across the region, including a ~N-S transect along Ellesmere Island. The majority of measurements indicate a
fast-polarisation orientation that parallels tectonic trends and boundaries, suggesting that lithospheric deformation is the dominant source of seismic anisotropy in the High Arctic; however, a sublithospheric contribution cannot be ruled out. Beneath Resolute in the central Canadian Arctic, distinct back-azimuthal variations in splitting parameters can be explained by two anisotropic layers. The upper layer is oriented ~E-W and correlates with tectonic trends and the inferred lithospheric deformation history of the region. The lower layer has a
~NNE-SSW orientation and may arise from present-day convective mantle flow beneath locally-thinned continental lithosphere. In addition to inferences of anisotropic structure beneath the Canadian High Arctic, measurements from the far north of our study region suggest the presence of an anisotropic zone in the lowermost mantle beneath northwest Alaska.