Imaging the Great Plains of the Central U.S. using Finite-Frequency Rayleigh Wave Tomography and Implications for Asthenosphere-Driven Uplift

Abstract:

Here we present a 3D shear velocity model for the lower crust and upper mantle beneath the Great Plains region in the central United States using finite frequency Rayleigh wave travel time tomography. We use USArray Transportable Array (TA) vertical component recording of teleseismic Rayleigh waves that we first invert for phase velocity using the modified two-plane wave method with finite frequency kernels. We then invert the resulting dispersion curves for shear velocity structure. Our analysis includes a characterization of the lithospheric structure in this tectonically transitional regime to illuminate the differences between the actively deforming western US and the stable continental interior of the northeastern Great Plains. The west is defined by slow velocities and thin lithosphere, whereas the east has fast velocities and thick lithosphere, with the thickest lithosphere in the northeast, representing the southwestern keel of the Superior craton. The Great Plains, which abut the Rocky Mountain Front, have an unusual elevation profile that possesses a much broader region of uplifted elevation and lower relief than other orogenic systems (Eaton 2009). From our tomography and regional heat flow data, we infer warm temperatures in the west and suggest that the asthenospheric mantle contributes to anomalously high elevation of the westernmost Great Plains with some secondary contribution due to crustal effects.