Lithospheric Structure Across the Northern Canadian Cordillera from Teleseismic Receiver Functions

English Abstract:

The composition and thickness of the crust and underlying mantle are important parameters that reflect the evolution and deformation of the lithosphere. In the northern Canadian Cordillera, these properties are poorly known due to sparse coverage of broadband seismic stations. In this work we characterize the structure of the crust and mantle across the northern Canadian Cordillera using data form a portable array of stations (CANOE array) The teleseismic data recorded by these broadband stations were used to perform receiver function analysis. These data indicate the presence of anisotropy or dipping reflectors in the crustal structure of the northern Cordillera observed in azimuthal variations of transverse component receiver functions. We provide a quantitative interpretation of receiver functions in terms of anisotropy or dipping structure by decomposing the azimuthal variations of depth migrated receiver functions into azimuthal harmonics. This technique can be used to map out the orientation of anisotropy that may be related to cracks and/or rock texture caused by deformation. We further show how crustal thickness varies along the array from the interior of the Cordillera to the adjacent Canadian Shield. These results show that crustal thickness is ~35 km thick on average, supporting the thesis that the high-elevation Cordillera is isostatically supported by the thermal buoyancy of the hot underlying mantle.