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Is complex fault zone behaviour a reflection of rheological heterogeneity?

Fagereng, Å and Beall, A. 2021. Is complex fault zone behaviour a reflection of rheological heterogeneity? Philosophical Transactions A: Mathematical, Physical and Engineering Sciences 379 (2193) , 20190421. 10.1098/rsta.2019.0421

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Abstract

Fault slip speeds range from steady plate boundary creep through to earthquake slip. Geological descriptions of faults range from localized displacement on one or more discrete planes, through to distributed shearing flow in tabular zones of finite thickness, indicating a large range of possible strain rates in natural faults. We review geological observations and analyse numerical models of two-phase shear zones to discuss the degree and distribution of fault zone heterogeneity and effects on active fault slip style. There must be certain conditions that produce earthquakes, creep and slip at intermediate velocities. Because intermediate slip styles occur over large ranges in temperature, the controlling conditions must be effects of fault properties and/or other dynamic variables. We suggest that the ratio of bulk driving stress to frictional yield strength, and viscosity contrasts within the fault zone, are critical factors. While earthquake nucleation requires the frictional yield to be reached, steady viscous flow requires conditions far from the frictional yield. Intermediate slip speeds may arise when driving stress is sufficient to nucleate local frictional failure by stress amplification, or local frictional yield is lowered by fluid pressure, but such failure is spatially limited by surrounding shear zone stress heterogeneity.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Additional Information: This article is part of a discussion meeting issue ‘Understanding earthquakes using the geological record’. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/ by/4.0/.
Publisher: Royal Society, The
ISSN: 1364-503X
Date of First Compliant Deposit: 10 September 2020
Date of Acceptance: 18 August 2020
Last Modified: 10 Feb 2021 14:21
URI: http://orca.cardiff.ac.uk/id/eprint/134771

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