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Seismic properties of the Nazca oceanic crust in southern Peruvian subduction system

Kim, YoungHee and Clayton, Robert W. (2015) Seismic properties of the Nazca oceanic crust in southern Peruvian subduction system. Earth and Planetary Science Letters, 429 . pp. 110-121. ISSN 0012-821X. http://resolver.caltech.edu/CaltechAUTHORS:20151022-152559100

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Abstract

The horizontal Nazca slab, extending over a distance of ∼800 km along the trench is one of enigmatic features in Peruvian subduction zone. Increased buoyancy of the oceanic lithosphere alone due to the subduction of Nazca Ridge is insufficient to fully explain such a lengthy segment. We use data from the recent seismic experiment in southern Peru to find that the subduction-related hydration plays a major role in controlling shear wave velocities within the upper part of the oceanic crust and overlying materials. We observe substantial velocity reductions of ∼20–40% near the top plate interface along- and perpendicular-to the trench from ∼40–120 km depths. In particular, significant shear wave velocity reductions and subsequently higher P-to-S velocity ratio (exceeding 2.0) at the flat slab region suggest that the seismically probed layer is fluid-rich and mechanically weak. The dominant source of fluid comes from metasediments and subducted crust (Nazca Ridge). Long-term supply of fluid from the southward migrating Nazca Ridge provides additional buoyancy of the subducting oceanic lithosphere and also lowers the viscosity of the overlying mantle wedge to drive and sustain the flat plate segment of ∼800 km along the trench. Also, by comparing calculated seismic velocities with experimentally derived mineral physics data, we additionally provide mechanical constraints on the possible changes in frictional behavior across the subduction zone plate interface. Observed low seismic velocities in the seismogenic zone suggest a presence of low strength materials that may be explained by overpressured pore fluids (i.e., accreted sediment included in the subduction channel).


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.epsl.2015.07.055DOIArticle
http://www.sciencedirect.com/science/article/pii/S0012821X15004987PublisherArticle
ORCID:
AuthorORCID
Clayton, Robert W.0000-0003-3323-3508
Additional Information:© 2015 Elsevier B.V. Received 22 April 2015; Received in revised form 16 July 2015; Accepted 24 July 2015; Available online 14 August 2015. This work was supported by the National Research Foundation of Korea Grant funded by the Korean Government(NRF-2014S1A2A2027609), and by the Korea Meteorological Ad-ministration Research and Development Program under Grant KMIPA2015-7020. We thank H. Lim from Seoul National University for extracting plate interface depths from the four published slab geometry models (in Fig.2a). We thank Y. Ma from Cal-tech for discussion on the data, and M. Chlieh from Université de Nice Sophia-Antipolis for providing the data for slip distribu-tion of four large megathrust events in southern Peru from his paper (Chliehetal.,2011). We thank the PeruSE project for supplying the seismic data used. Finally, we thank Editor P. Shearer, N. Piana Agostinetti, and one anonymous reviewer for thoughtful comments, which helped improve the manuscript.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
National Research Foundation of KoreaNRF-2014S1A2A2027609
Korea Meteorological AdministrationKMIPA2015-7020
Subject Keywords:subduction geometry; southern Peruvian subduction dynamics; Nazca Ridge; receiver function; mineralogy; slab hydration
Record Number:CaltechAUTHORS:20151022-152559100
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20151022-152559100
Official Citation:YoungHee Kim, Robert W. Clayton, Seismic properties of the Nazca oceanic crust in southern Peruvian subduction system, Earth and Planetary Science Letters, Volume 429, 1 November 2015, Pages 110-121, ISSN 0012-821X, http://dx.doi.org/10.1016/j.epsl.2015.07.055. (http://www.sciencedirect.com/science/article/pii/S0012821X15004987)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:61454
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:22 Oct 2015 22:38
Last Modified:31 Jan 2017 20:37

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