Eaton, David W.Maiti, Tannistha2018-10-192018-10-192018-10-19http://hdl.handle.net/1880/108906The Moho and lithosphere-asthenosphere boundary (LAB) are fundamental discontinuities in the Earth’s outermost layers. The structure of these features can be discerned using seismic methods, providing important insights into the tectonic history of a region. This thesis is focused on the structure of these discontinuities in and around cratons, which are large, coherent domains of Earth’s continental lithosphere that have attained long-term stability with little internal deformation. The receiver-function method is an approach that uses locally scattered waves to image discontinuity structure beneath a seismograph station. P-wave receiver functions (PRFs) are often used to study Moho characteristics. Here, synthetic PRFs are used to understand the nature of the Moho in different scenarios. This approach is applied to observations from EarthScope Transportable Array (TA) stations in the western U.S. within a region that exhibits a complex transition from the craton and the Cordillera. Beneath the Cordillera, a flat Moho is interpreted to reflect lower crustal channel flow, whereas beneath the North American craton the Moho exhibits greater structural relief. By definition, the LAB forms the lower boundary of a tectonic plate. Using geophysical imaging methods, the LAB is not as easily mapped as the Moho, leading to the use of various proxies, such as a boundary between layers with differing seismic anisotropy. In the upper mantle, seismic anisotropy is generated by lattice-preferred orientation of constituent minerals, especially olivine. A numerical-simulation approach is employed based on a self-consistent model that extends from the Earth’s surface to the mantle transition zone. Mantle flow is investigated by 3-D numerical solution of the boundary-value problem using a finite-element method. The flow velocity is converted to anisotropic elastic stiffness tensors to create an anisotropic model with 21 independent c ijkl parameter plus density. Teleseismic P and S wavefields are simulated using a finite-difference method to characterize mantle discontinuities. P and S wave receiver functions are computed using the synthetic waveforms to understand the effectiveness and limitations of these approaches for imaging the LAB. Anisotropy has a strong influence, due to change in S wave velocity in radial and transverse directions.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.numerical modellinglithosphere asthenosphere boundaryP-wave receiver functionS-wave receiver functionMoho transitionGeophysicsdoctoral thesis10.11575/PRISM/33218