Much information about the North American lithosphere has been gained by imaging seismic wave velocities. Additional constraints on the state of the subsurface can be gained by studying seismic attenuation, which has different sensitivity to physical properties. We produce a model of lateral variations in attenuation across the conterminous U.S. by analyzing P waveforms from deep earthquakes recorded by the EarthScope Transportable Array using a time-domain waveform matching approach. We divide the study area into 12 overlapping tiles and differential attenuation is measured in each tile independently; with analysis being repeated independently for 4 of the tiles. Measurements are combined into a smooth map using a linear inversion. Comparing results for adjacent tiles and for repeated tiles shows that the imaged features are robust. The final map is produced by combining all the measurements and shows generally higher attenuation west of the Rocky Mountain Front than east of it, with significant small length scale variations superimposed on that broad pattern. In general, there is a strong anticorrelation between differential attenuation and shear wave velocities at 90 km depth. However, a given change in velocity may correspond to large or small change in attenuation, depending on the area; suggesting that different physical mechanisms are operating. In some cases, most notably in the Snake River Plain, attenuation and velocity do not show the expected anticorrelation. The southern Intermountain Seismic Belt coincides with a high gradient in the attenuation signal, but even larger gradients further inland do not show any association with seismicity.

The Wyoming Craton underwent tectonic modifications during the Laramide Orogeny, which resulted in a series of basement-cored uplifts that built the modern-day Rockies. The easternmost surface expression of this orogeny - the Black Hills in South Dakota - is separated from the main trend of the Rocky Mountains by the southern half of the Powder River Basin, which we refer to as the Thunder Basin. Seismic tomography studies reveal a high-velocity anomaly which extends to a depth of ~300 km below the basin and may represent a lithospheric keel. We constrain seismic attenuation to investigate the hypothesis that the variations in lithospheric thickness resulted in the localization of stress and therefore deformation. We utilize data from the CIELO seismic array, a linear array that extends from east of the Black Hills across the Thunder Basin and westward into the Owl Creek Mountains, the BASE FlexArray deployment centered on the Bighorn Mountains, and the EarthScope Transportable Array. We analyze seismograms from deep teleseismic events and compare waveforms in the time-domain to characterize lateral varations in attenuation. Bayesian inversion results reveal high attenuation in the Black Hills and Bighorn Mountains and low attenuation in the Thunder and Bighorn basins. Scattering is rejected as an confounding factor because of a strong anticorrelation between attenuation and the amplitude of P wave codas. The results support the hypothesis that lateral variations in lithospheric strength, as evidenced by our seismic attenuation measurements, played an important role in the localization of deformation and orogenesis during the Laramide Orogeny.