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Crust and Upper Mantle Seismic Anisotropy Variations from the Coast to Inland in Central and Southern Mexico

Castellanos, Jorge and Pérez-Campos, Xyoli and Valenzuela, Raúl and Husker, Allen and Ferrari, Luca (2017) Crust and Upper Mantle Seismic Anisotropy Variations from the Coast to Inland in Central and Southern Mexico. Geophysical Journal International, 210 (1). pp. 360-374. ISSN 0956-540X. http://resolver.caltech.edu/CaltechAUTHORS:20170509-122332119

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Abstract

Subduction zones are among the most dynamic tectonic environments on Earth. Deformation mechanisms of various scales produce networks of oriented structures and faulting systems that result in a highly anisotropic medium for seismic wave propagation. In this study, we combine shear wave splitting inferred from receiver functions and the results from a previous SKS-wave study to quantify and constrain the vertically averaged shear wave splitting at different depths along the 100-station MesoAmerican Subduction Experiment array. This produces a transect that runs perpendicular to the trench across the flat slab portion of the subduction zone below central and southern Mexico. Strong anisotropy in the continental crust is found below the Trans-Mexican Volcanic Belt (TMVB) and above the source region of slow-slip events. We interpret this as the result of fluid/melt ascent. The upper oceanic crust and the overlying low-velocity zone exhibit highly complex anisotropy, while the oceanic lower crust is relatively homogeneous. Regions of strong oceanic crust anisotropy correlate with previously found low V_p/V_s regions, indicating that the relatively high V_s is an anisotropic effect. Upper-mantle anisotropy in the southern part of the array is in trench-perpendicular direction, consistent with the alignment of type-A olivine and with entrained subslab flow. The fast polarization direction of mantle anisotropy changes to N–S in the north, likely reflecting mantle wedge corner flow perpendicular to the TMVB.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1093/gji/ggx174DOIArticle
https://academic.oup.com/gji/article-lookup/doi/10.1093/gji/ggx174PublisherArticle
Additional Information:© 2017 The Author. Published by Oxford University Press on behalf of The Royal Astronomical Society. Accepted 2017 April 26. Received 2017 April 24; in original form 2015 October 4. Published: 27 April 2017. We thank the editor Saskia Goes and an anonymous reviewer whose comments greatly improved this manuscript. We thank the MASE team that installed and maintained MASE stations. Funding was possible through projects Conacyt 177676 and UNAM-PAPIIT IN110913. The first author had a scholarship from Conacyt.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
Consejo Nacional de Ciencia y Tecnología (CONACYT)177676
Universidad Nacional Autónoma de México (UNAM)IN110913
Subject Keywords:North America; Seismic anisotropy; Subduction zone processes
Record Number:CaltechAUTHORS:20170509-122332119
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170509-122332119
Official Citation:Jorge Castellanos, Xyoli Pérez-Campos, Raúl Valenzuela, Allen Husker, Luca Ferrari; Crust and upper-mantle seismic anisotropy variations from the coast to inland in central and Southern Mexico. Geophys J Int 2017; 210 (1): 360-374. doi: 10.1093/gji/ggx174
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77302
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 May 2017 22:39
Last Modified:02 Jun 2017 21:33

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