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Lithospheric radial anisotropy beneath the Gulf of Mexico

Chu, Risheng and Ko, Justin Yen-Ting and Wei, Shengji and Zhan, Zhongwen and Helmberger, Don (2017) Lithospheric radial anisotropy beneath the Gulf of Mexico. Earth and Planetary Science Letters, 466 . pp. 43-52. ISSN 0012-821X. doi:10.1016/j.epsl.2017.02.040.

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The Lithosphere–Asthenosphere Boundary (LAB), where a layer of low viscosity asthenosphere decouples with the upper plate motion, plays an essential role in plate tectonics. Most dynamic modeling assumes that the shear velocity can be used as a surrogate for viscosity which provides key information about mantle flow. Here, we derive a shear velocity model for the LAB structure beneath the Gulf of Mexico allowing a detailed comparison with that beneath the Pacific (PAC) and Atlantic (ATL). Our study takes advantage of the USArray data from the March 25th, 2013 Guatemala earthquake at a depth of 200 km. Such data is unique in that we can observe a direct upward traveling lid arrival which remains the first arrival ahead of the triplications beyond 18°. This extra feature in conjunction with upper-mantle triplication sampling allows good depth control of the LAB and a new upper-mantle seismic model ATM, a modification of ATL, to be developed. ATM has a prominent low velocity zone similar to the structure beneath the western Atlantic. The model contains strong radial anisotropy in the lid where V_(SH) is about 6% faster than V_(SV). This anisotropic feature ends at the bottom of the lithosphere at about the depth of 175 km in contrast to the Pacific where it extends to over 300 km. Another important feature of ATM is the weaker velocity gradient from the depth of 175 to 350 km compared to Pacific models, which may be related to differences in mantle flow.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ko, Justin Yen-Ting0000-0003-1523-4494
Zhan, Zhongwen0000-0002-5586-2607
Additional Information:© 2017 Elsevier B.V. Received 17 August 2016, Revised 19 February 2017, Accepted 21 February 2017, Available online 17 March 2017. The IRIS Data Management Center provided data used in this study. This work was supported by funding from the Strategic Priority Research Program (B) of Chinese Academy of Sciences through grant XDB18010304, the National Basic Research Program of China (973 Program) through grant 2013CB733203, and Natural Science Foundation of China through grant 41322027. Don Helmberger, Zhongwen Zhan and Justin Ko were supported by NSF (US) grant EAR-1358646. We thank Priscilla McLean for her help in preparing this manuscript.
Group:Seismological Laboratory
Funding AgencyGrant Number
Chinese Academy of SciencesXDB18010304
National Basic Research Program of China2013CB733203
Natural Science Foundation of China41322027
Subject Keywords:radial anisotropy; lithosphere; Gulf of Mexico; USArray; waveform modeling
Record Number:CaltechAUTHORS:20170317-142305531
Persistent URL:
Official Citation:Risheng Chu, Justin Yen-Ting Ko, Shengji Wei, Zhongwen Zhan, Don Helmberger, Lithospheric radial anisotropy beneath the Gulf of Mexico, Earth and Planetary Science Letters, Volume 466, 15 May 2017, Pages 43-52, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75211
Deposited By: Tony Diaz
Deposited On:24 Mar 2017 14:41
Last Modified:15 Nov 2021 16:31

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