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From slow to fast faulting: recent challenges in earthquake fault mechanics

Nielsen, S.

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Abstract

Faults—thin zones of highly localized shear deformation in the Earth—accommodate strain on a momentous range of dimensions (millimetres to hundreds of kilometres for major plate boundaries) and of time intervals (from fractions of seconds during earthquake slip, to years of slow, aseismic slip and millions of years of intermittent activity). Traditionally, brittle faults have been distinguished from shear zones which deform by crystal plasticity (e.g. mylonites). However such brittle/plastic distinction becomes blurred when considering (i) deep earthquakes that happen under conditions of pressure and temperature where minerals are clearly in the plastic deformation regime (a clue for seismologists over several decades) and (ii) the extreme dynamic stress drop occurring during seismic slip acceleration on faults, requiring efficient weakening mechanisms. High strain rates (more than 104 s−1) are accommodated within paper-thin layers (principal slip zone), where co-seismic frictional heating triggers non-brittle weakening mechanisms. In addition, (iii) pervasive off-fault damage is observed, introducing energy sinks which are not accounted for by traditional frictional models. These observations challenge our traditional understanding of friction (rate-and-state laws), anelastic deformation (creep and flow of crystalline materials) and the scientific consensus on fault operation. This article is part of the themed issue ‘Faulting, friction and weakening: from slow to fast motion’.

Citation

Nielsen, S. (2017). From slow to fast faulting: recent challenges in earthquake fault mechanics. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 375(2103), Article 20160016. https://doi.org/10.1098/rsta.2016.0016

Journal Article Type Article
Acceptance Date Jul 3, 2017
Online Publication Date Aug 21, 2017
Publication Date Aug 21, 2017
Deposit Date Oct 11, 2017
Publicly Available Date Mar 29, 2024
Journal Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences.
Print ISSN 1364-503X
Electronic ISSN 1471-2962
Publisher The Royal Society
Peer Reviewed Peer Reviewed
Volume 375
Issue 2103
Article Number 20160016
DOI https://doi.org/10.1098/rsta.2016.0016

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