Attenuation of Lg in the western US using the USArray

The unprecedented breadth and density of the USArray allows us to resolve lateral variations of 1-Hz Lg attenuation to 0.5 degrees over much of the western United States. We collected over 31,000 Lg amplitudes from 547 events and 408 stations of the initial USArray footprint. Two-dimensional tomographic inversion yielded Q ranging from 60 to 550, with a variance reduction of 47% relative to the best-fit constant Q model (Q=155). Q is low over most of the region, with lowest values associated with recent volcanic activity, and active shear zones. High Q is found in older, stable crust, notably the Colorado and Columbia plateaus, while smaller islands of high Q are associated with batholiths, including the Sierra Nevada, Peninsular, and Bitterroot Ranges, the western Mojave, and Okanogan Highlands, as well as other areas of competent crust such as the Harcuvar range, and two topographically bounded blocks in the Basin and Range.