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Intraslab seismicity and thermal stress in the subducted Cocos plate beneath central Mexico

Manea, Vlad and Manea, Marina and Kostoglodov, Vladimir and Sewell, Granville (2006) Intraslab seismicity and thermal stress in the subducted Cocos plate beneath central Mexico. Tectonophysics, 420 (3-4). pp. 389-408. ISSN 0040-1951. doi:10.1016/j.tecto.2006.03.029.

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We present a model of the subducting Cocos slab beneath Central Mexico, that provides an explanation for stresses causing the occurrence of the majority of the intraslab earthquakes which are concentrated in a long flat segment. Based on the recently developed thermal models for the Central Mexico subduction zone, the thermal stresses due to non-uniform temperature contrast in the subducting slab are calculated using a finite element approach. The slab is considered purely elastic but due to high temperature at its bottom the behavior is considered as ductile creep. The calculation results show a ∼ 20 km slab core characterized by a tensional state of stress with stresses up to 70 MPa. On the other hand, the top of the slab experiences high compressive thermal stresses up to 110 MPa, depending on the elastic constants used and location along the flat part of the subducting plate. These compressive stresses at the top of the slab are not consistent with the exclusive normal fault intraslab earthquakes, and two different sources of stress are proposed. The trenchward migration of the Mexican volcanic arc for the last 7 Ma indicates an increase of the slab dip through time. This observation suggests that the gravity torque might exceed the suction torque. Considering the flat slab as an embedded plate subject to an applied clockwise net torque of 0.5 × 10^(16)–1.5 × 10^(16) N m, the upper half would exhibit tensional stresses of 40–110 MPa that can actually balance the compressive thermally induced stresses. An alternative stress source might come from the slab pull force caused by the slab positive density anomaly. Based on our density anomaly estimations (75 ± 20 kg/m^3), a 350 km slab length, dipping at 20° into the asthenosphere, induces a slab pull force of 1.7 × 10^(12)–4.6 × 10^(12) N m. This force produces a tensional stress of 41–114 MPa, sufficient to balance the compressive thermal stresses at the top of the flat slab. The linear superposition of the thermally and torque or slab pull induced stresses shows tensile stresses up to 60–180 MPa inside the flat slab core. Also, our results suggest that the majority of the intraslab earthquakes inside the flat slab are situated where the resultant stresses are larger than 40–80 MPa. This study provides a reasonable explanation for the existence of exclusively normal fault intraslab earthquakes in the flat slab beneath Central Mexico, and also it shows that thermal stresses due to non-uniform reheating of subducting slabs play a considerable role in the total stress field.

Item Type:Article
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URLURL TypeDescription
Kostoglodov, Vladimir0000-0001-7169-3121
Additional Information:© 2006 Elsevier B.V. Received 20 June 2004, Revised 29 December 2005, Accepted 22 March 2006, Available online 9 June 2006. Helpful critical comments and constructive suggestions by Patrick Scheffmann, Kevin Furlong, Jeroen van Hunen, and one anonymous reviewer were used to improve the manuscript. This study was supported by CONACYT (Consejo Nacional de Ciencia y Technología) Grants G25842-T and 37293-T and by PAPIIT (Programa de Apoyo a Proyectos de Investigación e Innovación Technológica) Grant IN104801. We also like to acknowledge support from the Gordon and Betty Moore Foundation. This is a contribution 9145 of the Division of Geological and Planetary Sciences, CALTECH.
Group:Seismological Laboratory
Funding AgencyGrant Number
Consejo Nacional de Ciencia y TechnologíaG25842-T
Consejo Nacional de Ciencia y Technología37293-T
Programa de Apoyo a Proyectos de Investigación e Innovación TechnológicaIN104801
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:Thermal stress; Torque balance; Slab pull; Flat subduction; Mexican subduction zone
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Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences9145
Issue or Number:3-4
Record Number:CaltechAUTHORS:20170427-111249564
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Official Citation:Vlad Manea, Marina Manea, Vladimir Kostoglodov, Granville Sewell, Intraslab seismicity and thermal stress in the subducted Cocos plate beneath central Mexico, Tectonophysics, Volume 420, Issues 3–4, 7 July 2006, Pages 389-408, ISSN 0040-1951, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77006
Deposited By: Tony Diaz
Deposited On:27 Apr 2017 22:03
Last Modified:15 Nov 2021 17:04

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