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A dipping, thick segment of the Farallon Slab beneath Central US

Sun, Daoyuan and Gurnis, Michael and Saleeby, Jason and Helmberger, Don (2017) A dipping, thick segment of the Farallon Slab beneath Central US. Journal of Geophysical Research. Solid Earth, 122 (4). pp. 2911-2928. ISSN 2169-9313. doi:10.1002/2016JB013915.

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It has been hypothesized that much of the crustal deformation attributed to the Laramide orogeny of the southwest North American Cordillera was caused by dynamic effects induced by the flat subduction of a large oceanic plateau that was embedded within the Farallon plate. Previous studies have identified within the North American mantle a seismic velocity anomaly that plausibly represents the remnants of the subducted plateau. Coupled plate kinematic and dynamic modeling of the anomaly, as well as surface geological findings identify this anomaly as the subducted conjugate to the Shatsky Rise. Here, we find clear evidence for a northeastward dipping (35° dip), thick (up to 400 km thick) slab-like seismic velocity anomaly within the top of the lower mantle below the central United States. Using a deep focus earthquake below Spain, we find that the observed seismic waveforms recorded with the dense USArray display multi-pathing indicative of sharp surfaces. Plate tectonic reconstructions in which the anomaly is migrated back in time suggest strong coupling of the plateau-thickened slab segment to the overriding North America Plate as it was subducted. In combination with the reconstructions, we interpret the structure as arising from eastward dipping Farallon subduction at the western margin of North America during the Cretaceous, in contrast with some recent interpretations. It appears that the plateau area of the slab has been further thickened, which might undergo a combination of pure shear bulk shortening during flat-slab subduction and/or by a folding instability during penetration into the lower mantle.

Item Type:Article
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URLURL TypeDescription
Sun, Daoyuan0000-0003-4461-4664
Gurnis, Michael0000-0003-1704-597X
Additional Information:© 2017 American Geophysical Union. Received 29 DEC 2016; Accepted 25 MAR 2017; Accepted article online 28 MAR 2017; Published online 20 APR 2017. The authors would like to thank the Editor Yehuda Ben-Zion, Associate Editor, Nathan Simmons, Jeroen Ritsema, Wim Spakman, and two anonymous reviewers. Their suggestions and comments were greatly appreciated and lead to significant improvements to the manuscript. Data are provided by IRIS data center and Earthscope USArray, which are available at All maps in this paper were produced using GMT developed by Paul Wessel and Walter H. F. Smith. D.S. supported by Strategic Priority Research Program (B) of Chinese Academy of Sciences, grant XDB18000000, the Fundamental Research Funds for the Central Universities in China WK2080000078, National Natural Science Foundation of China 41574037, and Key Research Program of Frontier Sciences CAS, grant QYZDB-SSW-SYS011. M.G. and D.V.H. supported by NSF grant EAR-1358646. Additional support for M.G. provided by NSF grant EAR-1247022.
Group:Seismological Laboratory
Funding AgencyGrant Number
Chinese Academy of SciencesXDB18000000
Fundamental Research Funds for the Central Universities in ChinaWK2080000078
National Natural Science Foundation of China41574037
Chinese Academy of SciencesQYZDB-SSW-SYS011
Subject Keywords:Farallon slab; waveform modeling
Issue or Number:4
Record Number:CaltechAUTHORS:20170329-090559845
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Official Citation:Sun, D., M. Gurnis, J. Saleeby, and D. Helmberger (2017), A dipping, thick segment of the Farallon Slab beneath central U.S., J. Geophys. Res. Solid Earth, 122, 2911–2928, doi:10.1002/2016JB013915
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75503
Deposited By: Tony Diaz
Deposited On:05 Apr 2017 16:21
Last Modified:15 Nov 2021 16:34

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