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Hydrous oceanic crust hosts megathrust creep at low shear stresses

Tulley, Christopher J., Fagereng, Åke and Ujiie, Kohtaro 2020. Hydrous oceanic crust hosts megathrust creep at low shear stresses. Science Advances 6 (22) , eaba1529. 10.1126/sciadv.aba1529

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Abstract

The rheology of the metamorphosed oceanic crust may be a critical control on megathrust strength and deformation style. However, little is known about the strength and deformation style of metamorphosed basalt. Exhumed megathrust shear zones exposed on Kyushu, SW Japan, contain hydrous metabasalts deformed at temperatures between ~300° and ~500°C, spanning the inferred temperature-controlled seismic-aseismic transition. Field and microstructural observations of these shear zones, combined with quartz grain-size piezometry, indicate that metabasalts creep at shear stresses <100 MPa at ~370°C and at shear stresses <30 MPa at ~500°C. These values are much lower than those suggested by viscous flow laws for basalt. The implication is that relatively weak, hydrous, metamorphosed oceanic crust can creep at low viscosities over a wide shear zone and have a critical influence on plate interface strength and deformation style around the seismic-aseismic transition.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Additional Information: This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) licence
Publisher: American Association for the Advancement of Science
ISSN: 2375-2548
Date of First Compliant Deposit: 11 June 2020
Date of Acceptance: 19 March 2020
Last Modified: 06 Oct 2020 01:29
URI: http://orca-mwe.cf.ac.uk/id/eprint/132348

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