Title

Lithospheric Layering Beneath the Contiguous United States Constrained by S-To-P Receiver Functions

Abstract

To image upper mantle seismic discontinuities beneath the contiguous United States, a total of 284,121 S-to-P receiver functions (SRFs) recorded by 3,594 broadband seismic stations in the EarthScope Transportable Array and other permanent and temporary deployments are stacked in circular bins of 2° in radius. A robust negative arrival, representing a sharp discontinuity of wave speed reduction with depth, is visible in virtually all the stacked traces in the depth range of 30–110 km. Beneath the western U.S., the mean depth of this discontinuity is 69 ± 17 km, and beneath the eastern U.S., it is 76 ± 5 km, both are comparable to the depth of the tomographically-determined lithosphere–asthenosphere boundary (LAB). In contrast, the depth of the discontinuity beneath the stable cratonic region of the central U.S. is 87 ± 6 km, which is significantly shallower than the ∼250 km LAB depth determined by seismic tomography. Based on the amplitude of the corresponding arrival in the SRFs and findings from previous seismic tomography and mantle xenolith studies, this discontinuity beneath the central U.S. is interpreted as the top of an intra-lithospheric low wave speed, probably phlogopite-rich layer. The observations provide new constraints on a number of regional scale tectonic processes, such as lithospheric stretching in the Texas–Louisiana Gulf Coastal Plain and the Basin and Range Province, and possible lithospheric basal erosion beneath the northeastern U.S.

Department(s)

Geosciences and Geological and Petroleum Engineering

Comments

This study was partially supported by the China Scholarship Council to L.L. under contract 201408040006, and the United States National Science Foundation under grant 1460516 to S.G.

Keywords and Phrases

Continental crust; Lithosphere; Lithospheric thickness; Receiver function

International Standard Serial Number (ISSN)

0012-821X

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2018 Elsevier, All rights reserved.

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