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Coseismic fault lubrication by viscous deformation

Pozzi, Giacomo and De Paola, Nicola and Nielsen, Stefan and Holdsworth, Robert and Tesei, Telemaco and Thieme, Manuel and Demouchy, Sylvie (2021) 'Coseismic fault lubrication by viscous deformation.', Nature geoscience., 14 (6). pp. 437-442.


Despite the hazard posed by earthquakes, we still lack fundamental understanding of the processes that control fault lubrication behind a propagating rupture front and enhance ground acceleration. Laboratory experiments show that fault materials dramatically weaken when sheared at seismic velocities (>0.1 m s−1). Several mechanisms, triggered by shear heating, have been proposed to explain the coseismic weakening of faults, but none of these mechanisms can account for experimental and seismological evidence of weakening. Here we show that, in laboratory experiments, weakening correlates with local temperatures attained during seismic slip in simulated faults for diverse rock-forming minerals. The fault strength evolves according to a simple, material-dependent Arrhenius-type law. Microstructures support this observation by showing the development of a principal slip zone with textures typical of sub-solidus viscous flow. We show evidence that viscous deformation (at either sub- or super-solidus temperatures) is an important, widespread and quantifiable coseismic lubrication process. The operation of these highly effective fault lubrication processes means that more energy is then available for rupture propagation and the radiation of hazardous seismic waves.

Item Type:Article
Additional Information:A read-only copy of the Version of Record can be viewed at the following link, via Springer SharedIt:
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Date accepted:30 March 2021
Date deposited:07 April 2021
Date of first online publication:17 May 2021
Date first made open access:17 November 2021

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