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Seismicity and structure in central Mexico: Evidence for a possible slab tear in the South Cocos plate

Dougherty, Sara L. and Clayton, Robert W. (2014) Seismicity and structure in central Mexico: Evidence for a possible slab tear in the South Cocos plate. Journal of Geophysical Research. Solid Earth, 119 (4). pp. 3424-3447. ISSN 2169-9313. http://resolver.caltech.edu/CaltechAUTHORS:20140724-143520914

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Abstract

The morphology of the transition from flat to normal subduction in eastern central Mexico is explored using intraslab earthquakes recorded by temporary and permanent regional seismic arrays. Observations of a sharp transition in slab dip near the abrupt end of the Trans-Mexican Volcanic Belt (TMVB) suggest a possible slab tear located within the subducted South Cocos plate. The eastern lateral extent of a thin ultra-slow velocity layer (USL) imaged atop the Cocos slab in recent studies along the Meso America Subduction Experiment array is examined here using additional data. We find an end to this USL which is coincident with the western boundary of a zone of decreased seismicity and the end of the TMVB near the sharp transition in slab dip. Waveform modeling of the 2-D structure in this region using a finite difference algorithm provides constraints on the velocity and geometry of the slab's seismic structure and confirms the location of the USL. Analysis of intraslab seismicity patterns reveals clustering, sudden increase in depth, variable focal mechanism orientations and faulting types, and alignment of source mechanisms along the sharp transition in slab dip. The seismicity and structural evidence suggests a possible tear in the South Cocos slab. This potential tear, together with the tear along the Orozco Fracture Zone to the northwest, indicates a slab rollback mechanism in which separate slab segments move independently, allowing for mantle flow between the segments.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1002/2013JB010883 DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/2013JB010883/abstractPublisherArticle
http://onlinelibrary.wiley.com/doi/10.1002/2013JB010883/suppinfoPublisherSupporting Information
ORCID:
AuthorORCID
Clayton, Robert W.0000-0003-3323-3508
Additional Information:© 2014 American Geophysical Union. Received 2 DEC 2013; Accepted 6 APR 2014; Accepted article online 9 APR 2014; Published online 29 APR 2014; Corrected 2 JUL 2014. MASE and VEOX data are available at the IRIS DMC under the network code TO. Researchers should contact Michael Brudzinski for OXNET data and Carlos M. Valdes Gonzalez for SSN waveform data. The SSN event catalog is accessible from the Servicio Sismológico Nacional website (http:// www.ssn.unam.mx/). The SSN CMT catalog is available on the Mexican CMT Project website (http://laxdoru.igeofcu. unam.mx/cmt). The ISC Bulletin event catalog is accessible from the International Seismological Centre website (http://www.isc.ac.uk). This study was supported in part by the Gordon and Betty Moore Foundation through the Tectonics Observatory at California Institute of Technology. This is contribution 256 from the Caltech Tectonics Observatory. We are grateful to Michael Brudzinski, Enrique Cabral-Cano, and Alejandra Arciniega-Ceballos for making the OXNET waveform data available. We thank Arturo Iglesias for providing the Servicio Sismológico Nacional event catalog and Ting Chen for the slab isodepth contour lines. We also thank Editor Robert Nowack, the Associate Editor, Sebastiano D’Amico, and an anonymous reviewer for helpful comments, which improved the manuscript. Erratum: In the originally published version of this article two citations were missing. The error has since been corrected and this version may be considered the authoritative version of record.
Group:Caltech Tectonics Observatory, Seismological Laboratory
Funders:
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
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Caltech Tectonics Observatory256
Record Number:CaltechAUTHORS:20140724-143520914
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140724-143520914
Official Citation:Dougherty, S. L., and R. W. Clayton (2014), Seismicity and structure in central Mexico: Evidence for a possible slab tear in the South Cocos plate, J. Geophys. Res. Solid Earth, 119, 3424–3447, doi:10.1002/2013JB010883
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47476
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:24 Jul 2014 22:11
Last Modified:31 Jan 2017 20:43

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