Anisotropic upper-mantle stratigraphy and architecture of the Slave craton

The Earth's physical properties show a dominantly radial structure which is the result of compositional differentiation, isochemical phase changes(1) and rheological layering(2). Rheological layering is perhaps the most difficult to investigate using conventional seismological techniques because the seismic manifestation of this property, elastic anisotropy, may closely mimic the effects of isotropic heterogeneity(3). Nonetheless, an improved characterization of Earth's rheological structure promises important insights into such processes as plate dynamics and continental evolution. Here, I present a methodology for effectively characterizing sharp transitions in anisotropic, upper-mantle structure using the coda of teleseismic P-waves. Application to seismograms from the Slave craton reveals a well-developed stratigraphy, at least in part anisotropic, with major boundaries occurring at nominal depths of 75, 135 and 195 km. The geometry and sharpness of these discontinuities suggest a structural origin, perhaps involving shallow subduction.