Abstract

The amalgamation of crustal blocks that composes the western cordillera of North America has a long history of deformation across a broad zone. Investigations spanning a range of scales in the region have sought to unravel details of its structure and evolution. By sampling the entire western portion of the United States, the deployment of the Transportable Array component of the EarthScope USArray provides broadband seismic data to study crustal structure across much of this deforming region. Receiver functions recorded across the western United States provide insight into the thickness of the crust and how it varies between tectonic provinces. The thickness of the crust varies from <30 km in the southern Basin and Range and along the west coast to >50 km beneath the Rocky Mountains in Colorado and Wyoming. Distinct crustal structures characterize the Basin and Range, Snake River Plain, the Sierra Nevada, and the active Cascade volcanic arc, suggesting that the recent tectonic processes that affected the region have shaped the crustal structure. In addition, characteristics of the crust appear to relate to the boundaries of, and structures within, the terranes that formed North America. Patterns of crustal thickness across an expansive region presented here allow for the crustal response to specific tectonic processes to be determined while still imaging small-scale structures that can be more difficult to identify in a continental-scale study. This provides a context for previous and future detailed studies to understand how observed crustal structures relate to the evolution of western North America.

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