A reassessment of outer-rise seismicity and its implications for the mechanics of oceanic lithosphere

Craig, T. J. and Copley, A. and Jackson, J. (2014) A reassessment of outer-rise seismicity and its implications for the mechanics of oceanic lithosphere. Geophysical Journal International, 197 (1). pp. 63-89. ISSN 0956-540X DOI 10.1093/gji/ggu013

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Official URL: http://doi.org/10.1093/gji/ggu013

Abstract

We use body-waveform modelling to constrain the source parameters of earthquakes occurring globally in oceanic lithosphere beneath the subduction zone outer rise and outer trench slope. These data are then used to map the stress state in the lithosphere of the downgoing plate as it bends into the subduction zone. Our results provide new constraints on the faulting of oceanic lithosphere at the outer rise, which is important for understanding the transmission of plate-driving forces through the subduction system. In all cases, shallow normal-faulting earthquakes are observed at the top of the plate, and are separated in depth from any deeper thrust-faulting earthquakes. No temporal variation associated with large thrust-faulting earthquakes on the subduction interface is seen in the depth extent of each type of faulting at the outer rise. The transition depth from trench-normal extension to compression is found to vary in agreement with models in which deformation is driven by the combination of in-plane stresses and bending stresses, resulting principally from slab pull. Combining the seismologically derived constraints on the thickness of the elastic core of the plate with estimates of the plate curvature, we place upper bounds on the strength of the lithosphere at the outer rise, which is required to be ≲300 MPa for a constant yield stress model, or governed by an effective coefficient of friction of ≲0.3.

Item Type: Article
Uncontrolled Keywords: 2014AREP; IA67;
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
07 - Gold Open Access
Journal or Publication Title: Geophysical Journal International
Volume: 197
Page Range: pp. 63-89
Identification Number: 10.1093/gji/ggu013
Depositing User: Sarah Humbert
Date Deposited: 02 Dec 2016 13:48
Last Modified: 02 Dec 2016 13:48
URI: http://eprints.esc.cam.ac.uk/id/eprint/3767

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