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Thermomechanics of mid-ocean ridge segmentation

Choi, Eun-seo and Lavier, Luc and Gurnis, Michael (2008) Thermomechanics of mid-ocean ridge segmentation. Physics of the Earth and Planetary Interiors, 171 (1-4, S). pp. 374-386. ISSN 0031-9201. doi:10.1016/j.pepi.2008.08.010.

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The mechanics responsible for the initiation of the orthogonal pattern characterizing mid-ocean ridges and transform faults are studied using numerical models. The driving forces are thermal stresses arising from the cooling of young oceanic crust and extensional kinematic boundary conditions. Thermal stress can exert ridge-parallel tension comparable in magnitude to spreading-induced tension when selectively released by ridges and ridge-parallel structure. Two modes of ridge segment growth have been identified in plan view: an overlapping mode where ridge segments overlap and bend toward each other and a connecting mode where two ridge segments are connected by a transform-like fault. As the ratio of thermal stress to spreading-induced stress (γ) increases, the patterns of localized plastic strain change from the overlapping to connecting mode. The orthogonal pattern marks the transition from one mode to the other. Besides the amount of stress from each driving force, the rate of stress accumulation is crucial in determining the emergent pattern. This rate-dependence is characterized by the spreading rate normalized by a reference-cooling rate (Pe′). When Pe′ is paired with the ratio of thermal stress to the reference spreading-induced stress (γ′), they unambiguously define stability fields of the two modes. The obliquely connecting, the orthogonally connecting, and the overlapping mode are similar to ridge-transform fault intersections observed in ultra-slow, slow to intermediate, and fast spreading centers, respectively. The patterns are also sensitive to the strain weakening rate. Fracture zones were created in part as a response to thermal stress.

Item Type:Article
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Gurnis, Michael0000-0003-1704-597X
Additional Information:© 2008 Elsevier. Received 25 September 2007; revised 30 June 2008; accepted 4 August 2008. Available online 23 August 2008. This is contribution number 9149 of the Division of Geological and Planetary Sciences and 41 of the Tectonics Observatory. Development of SNAC was partially supported by the NSF ITR program under EAR-0205653. All calculations carried out on the Caltech Geosciences Supercomputer Facility partially supported by NSF EAR-0521699. Additional support provided through the Caltech Tectonics Observatory by the Gordon and Betty Moore Foundation.
Group:Caltech Tectonics Observatory, Seismological Laboratory
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:Mid-ocean ridge propagation; Ridge tip interaction; Thermal stress; Elasto-visco-plastic rheology
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Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences9149
Caltech Tectonics Observatory41
Issue or Number:1-4, S
Record Number:CaltechAUTHORS:CHOpepi08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12908
Deposited By: Archive Administrator
Deposited On:15 Jan 2009 21:01
Last Modified:08 Nov 2021 22:33

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