Evidence of Mantle‐Based Deformation Across the Western United States

Abstract

We investigate the role that upper mantle buoyancy anomalies play in determining the behavior of the crust. Recently, Castellanos et al. (2020; https://doi.org/10.1126/sciadv.abb0476) observed that the anisotropy of the Pacific Northwest (PNW) crust correlates with the upper-mantle velocity structure and suggested that vertical loads in the upper mantle can displace the Moho and drive crustal flow on a regional scale. To provide further insight into this relation, we resolve the crustal anisotropy in regions where near-surface mantle-based deformation might have occurred or is presently occurring. Specifically, we focus on the crust around the Rocky Mountains and around California since high-resolution tomographic images reveal the presence of mantle structures similar to the ones that are thought to be driving the crust in the PNW. Our results reveal crustal flow driven by mantle vertical loading in both regions and suggest that this mechanism may be key in maintaining crustal isostasy during an orogeny.

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