Examining Mantle Flow and Anisotropy under Southwest Alaska and Northwest Canada from Multi-layered Shear Wave Splitting

Abstract:

The complex tectonic setting created as the Pacific Plate subducts under Alaska and Canada, while the Yakutat terrane collides into the North America Plate, has been the focus of several careful seismic anisotropy studies (e.g. Christensen and Abers, 2010) in the last two decades. However, no study has focused on more than one layer of anisotropy when examining the seismic behavior in these areas. Given that mantle wedge flow may be different from sub-slab flow, it is worth constraining the anisotropy in this region in terms of multiple layers of potentially dipping anisotropy. Moreover, shear wave splitting patterns may give indications of the viscosity of the mantle wedge (Jadamec and Billen, 2012). In this study, the wealth of data collected over the last fifteen years will be used to constrain the orientations of multiple layers of anisostropy using the Cross-convolution method (Menke and Levin, 2003) combined with a new statistical approach that better quantifies confidence bounds in the presence of pre-SKS noise.