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The crust and uppermost mantle structure of Southern Peru from ambient noise and earthquake surface wave analysis

Ma, Yiran and Clayton, Robert W. (2014) The crust and uppermost mantle structure of Southern Peru from ambient noise and earthquake surface wave analysis. Earth and Planetary Science Letters, 395 . pp. 61-70. ISSN 0012-821X. doi:10.1016/j.epsl.2014.03.013.

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Southern Peru is located in the northern Central Andes, which is the highest plateau along an active subduction zone. In this region, the Nazca slab changes from normal to flat subduction, with the associated Holocene volcanism ceasing above the flat subduction regime. We use 6 s to 67 s period surface wave signals from ambient noise cross-correlations and earthquake data, to image the shear wave velocity (V_(SV) structure to a depth of 140 km. A mid-crust low-velocity zone is revealed, and is interpreted as partially molten rocks that are part of the Andean low-velocity zone. It is oblique to the present trench, and possibly indicates the location of the volcanic arcs formed during the steepening of the Oligocene flat slab beneath the Altiplano plateau. The recently subducted slab beneath the forearc shows a decrease in velocity from the normal to flat subduction regime that might be related to hydration during the formation of the Nazca ridge, which in turn may contribute to the buoyancy of the flat slab. The mantle above the flat slab has a comparatively high velocity, which indicates the lack of melting and thus explains the cessation of the volcanism above. A velocity contrast from crust to uppermost mantle is imaged across the Cusco–Vilcanota Fault System, and is interpreted as the boundary between two lithospheric blocks.

Item Type:Article
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URLURL TypeDescription
Ma, Yiran0000-0002-8369-3310
Clayton, Robert W.0000-0003-3323-3508
Additional Information:© 2014 Elsevier B.V. Received 17 December 2013, Revised 7 March 2014, Accepted 8 March 2014, Available online 4 April 2014. Editor: P. Shearer. We thank Prof. Huajian Yao for providing the ambient noise dispersion measurement code, Prof. Don Forsyth for providing the two-plane-wave tomography code, and Dunzhu Li for useful discussions. We also thank the editor and two anonymous reviewers for their helpful comments. This work is supported by NSF (EAR-1045683) and the Gordon and Betty Moore Foundation through the Tectonics Observatory at Caltech (contribution number 257).
Group:Caltech Tectonics Observatory, Seismological Laboratory, Division of Geological and Planetary Sciences
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Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:Central Andes; flat subduction; surface wave tomography
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Caltech Tectonics Observatory257
Record Number:CaltechAUTHORS:20140619-084953376
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Official Citation:Yiran Ma, Robert W. Clayton, The crust and uppermost mantle structure of Southern Peru from ambient noise and earthquake surface wave analysis, Earth and Planetary Science Letters, Volume 395, 1 June 2014, Pages 61-70, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46350
Deposited By: Ruth Sustaita
Deposited On:19 Jun 2014 16:20
Last Modified:10 Nov 2021 17:24

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