Strength of strained two-phase mixtures: Application to rapid creep and stress amplification in subduction zone mélange

Beall, Adam, Fagereng, Ake and Ellis, Susan 2019. Strength of strained two-phase mixtures: Application to rapid creep and stress amplification in subduction zone mélange. Geophysical Research Letters 46 (1) , pp. 169-178. 10.1029/2018GL081252

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Abstract

Aseismic creep may occur by distributed deformation in mélange shear zones comprising weak matrix and stronger clast materials. Slow slip events or steady tectonic displacement can be distributed over <100‐m thick shear zones if weak matrix controls bulk shear zone deformation. We use 2‐D numerical models to quantify the rheology of moderately strained (shear strain <1.75) mélange for various volumetric proportions of competent clasts. Mélange deformation with <50% clasts is matrix dominated and can accommodate steady creep. At higher clast proportions mélange viscosity increases more than tenfold after small strains, because strong clasts interact and form force chains. Clast shear stress is amplified above the imposed shear stress, by a factor of <14 where force chains develop. Slow slip events may occur due to a temporary absence of force chains, while localized regions of high shear stress generate coincident fracturing and potentially tremor events.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Ocean Sciences
Subjects:	Q Science > QE Geology
Publisher:	American Geophysical Union
ISSN:	0094-8276
Date of First Compliant Deposit:	30 January 2019
Date of Acceptance:	2 January 2019
Last Modified:	16 Apr 2019 13:52
URI:	http://orca.cf.ac.uk/id/eprint/118402

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