Nature of a low-velocity zone atop the transition zone in northwestern Canada ...

• Main Author: Schaeffer, Andrew John
• Format: Text
• Language: English
• Published: University of British Columbia 2009
• Subjects: Canada; Yellowknife
• Online Access: https://dx.doi.org/10.14288/1.0052946; https://doi.library.ubc.ca/10.14288/1.0052946

Seismic studies over the past decade have identified a S-wave low-velocity zone (LVZ) above the transition zone at various locations around the globe. This layer is hypothesized to be a lens of dense, fluid-rich silicate melt ponding atop the 410 km discontinuity, beneath the silicate melt-density crossover predicted to exist within the upper mantle. We have assembled a P- and S-receiver function (PRF and SRF, respectively) dataset from the CNSN Yellowknife Array (YKA), the CANOE array, and the POLARIS-Slave array, to quantify the physical properties and geographical extent of the layer in Northwestern Canada. In order to compute the Poisson's ratio, an important discriminant of possible composition and/or fluid content, we generated a suite of 1-D velocity models based on IASP91, but with varying thicknesses and velocity ratios for a hypothetical layer above the 410 km discontinuity. From these models we computed moveout curves for the range of slowness represented in the YKA data. A grid search was ...