Seismic anisotropy associated with continental lithosphere accretion beneath the CANOE array, northwestern Canada

摘要: We examine upper-mantle seismic anisotropy beneath the cordillera and craton of northwestern Canada using multi-event station averages shear-wave splitting SKS, SKKS, sSKS phases recorded during Canadian Northwest Experiment (CANOE). Splitting times derived from averaging at each range 0 to 1.4 s, with an array average ∼0.65 s. Over broad portions array, fast directions are coherent roughly consistent direction absolute plate motion in a hotspot reference frame, suggesting that asthenospheric fabric underlies much region. Within this framework, show marked variability over length scales 50–200km, generally correlated surface and/or crustal tectonics. Anomalous is observed across ancient suture within cratonic lithosphere, apparently associated complex dipping produced continental assembly. The deformation front Rockies correlates significant change behavior, demarking craton-cordillera transition mantle. small cordillera, indicating lithospheric weaker or less than craton. In western rotate abruptly parallel boundary, implying plate-boundary extends ∼200km into North American continent.