Lithospheric structue of Northern Canada from receiver functions.

Three-component seismograms from a number of stations in Canadian Northwestern Territories (NWT) and Nunavut province are assembled in order to investigate lithospheric and mantle structure below the Slave Province and around Hudson Bay. The arrival times of the phases converted from the 410-km and 660-km discontinuities are used to obtain the teleseismic P and S travel-time residuals that constrain velocity models. Receiver functions for P-waves (PRF) are inverted simultaneously with functions for S-wave (SRF) and with teleseismic travel time residuals for the crust and upper mantle models. For the stations, where residuals can not be identified, we use regional tomography data. The inversion provides robust results for the S-wave velocities in the crust and upper mante up to a depth of 300 km as well as constraints on the P-wave velocities and their ratio. In the models obtained we recognize the Moho, mid-lithospheric discontinuities, the LAB, the LVZ, and the Lehmann discontinuity. For the stations in the south of NWT we observe variations in crustal thickness from 30-35 to 40-50 km. For the upper mantle in this area Vs values are lower than expected for cratons, and Vp/Vs ratio in the uppermost mantle may indicate high fraction of Opx.