Western US seismic anisotropy revealing complex mantle dynamics

TitleWestern US seismic anisotropy revealing complex mantle dynamics
Publication TypeJournal Article
Year of Publication2018
AuthorsZhou Q., Hu J.S, Liu L.J, Chaparro T., Stegman DR, Faccenda M.
JournalEarth and Planetary Science Letters
Volume500
Pagination156-167
Date Published2018/10
Type of ArticleArticle
ISBN Number0012-821X
Accession NumberWOS:000445718700016
Keywordsazimuthal anisotropy; beneath; complex mantle dynamics; cratonic lithosphere; Farallon slab; flow; Geochemistry & Geophysics; hot mantle; intrusion; Juan de Fuca subduction; lattice preferred orientation; lithosphere; Olivine; Shear; slab; subduction zones; thickness variation; united-states; western US seismic anisotropy
Abstract

The origin of the complex pattern of SKS splitting over the western United States (U.S.) remains a long-lasting debate, where a model that simultaneously matches the various SKS features is still lacking. Here we present a series of quantitative geodynamic models with data assimilation that systematically evaluate the influence of different lithospheric and mantle structures on mantle flow and seismic anisotropy. These tests reveal a configuration of mantle deformation more complex than ever envisioned before. In particular, we find that both lithospheric thickness variations and toroidal flows around the Juan de Fuca slab modulate flow locally, but their co-existence enhances large-scale mantle deformation below the western U.S. The ancient Farallon slab below the east coast pulls the western U.S. upper mantle eastward, spanning the regionally extensive circular pattern of SKS splitting. The prominent E-W oriented anisotropy pattern within the Pacific Northwest reflects the existence of sustaining eastward intrusion of the hot Pacific oceanic mantle to beneath the continental interior, from within slab tears below Oregon to under the Snake River Plain and the Yellowstone caldera. This work provides an independent support to the formation of intra-plate volcanism due to intruding shallow hot mantle instead of a rising mantle plume. (C) 2018 Elsevier B.V. All rights reserved.

DOI10.1016/j.epsl.2018.08.015
Short TitleEarth Planet. Sci. Lett.
Student Publication: 
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