Interrogating Seismic Anisotropy using Receiver Functions – An Improved Understanding of Past Deformational Processes in Cratonic North America

Abstract:

Knowledge regarding the dynamics of Earth’s interior is critical to our understanding of both past and present tectonic processes. Unlike commonly used techniques such as shear wave splitting, anisotropic receiver function analysis yields both precise depth constraints on the source of anisotropy and can constrain non-horizontal axes of symmetry. Despite this, receiver functions are underutilized when it comes to examining sharp gradients in anisotropy. Here, we highlight recent methodological advances and results from using receiver functions to interrogate mantle anisotropy in different tectonic settings, with a specific focus on using anisotropic receiver function analysis to interrogate frozen-in anisotropy in the mantle lithosphere beneath continental North America. Previous receiver function results have revealed multiple mid-lithospheric discontinuities that correspond to sharp gradients in anisotropy, with a consistent N- to NW- orientation of anisotropy in the upper mantle lithosphere within the Granite-Rhyolite province. We expand upon this work by examining variations in frozen-in anisotropy across terrane boundaries, and utilizing a Markov chain Monte Carlo algorithm to model the orientation of anisotropy in the lithospheric mantle beneath long-running seismic stations. Ultimately, anisotropic receiver function analysis is an excellent tool for estimating the orientation of anisotropy at depth, and in this example, provides clues into the formation and evolution of cratonic North America.