Crustal anisotropy beneath Hudson Bay from ambient noise tomography: Evidence for post-orogenic lower-crustal flow?

摘要: The crust underlying Hudson Bay, Canada records a long and complex tectonic history. In this study, we investigate region using tomographic inversion based on continuous ambient noise recordings from 37 broadband seismograph stations that encircle Bay. data were processed to obtain group-velocity dispersion measurements 10–35 s period, which inverted an algorithm incorporates the effects of anisotropy. This work is among first in have been used azimuthal method uses smoothing damping regularize solution; due significantly increased number model parameters relative isotropic case, performed careful analysis for parameter selection determine whether “leakage” occurs between anisotropic parameters. We observe robust pattern fast directions mid-crust are consistent with large-scale trends magnetic-anomaly patterns. particular, distinctive double-indentor shape Superior craton clearly expressed both sets. breaks down deeper crust, suggesting some degree lithospheric decoupling lower such as channel flow, occurred during orogenesis. Given regional evidence vertically coherent deformation mantle, interpret overprint post-dates main phase Trans-Hudson deformation. At most levels profound change direction across inferred suture beneath