Fast-moving dislocations trigger flash weakening in carbonate-bearing faults during earthquakes

Rupture fronts can cause fault displacement, reaching speeds up to several ms(−1) within a few milliseconds, at any distance away from the earthquake nucleation area. In the case of silicate-bearing rocks the abrupt slip acceleration results in melting at asperity contacts causing a large reduction...

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Autores principales: Spagnuolo, Elena, Plümper, Oliver, Violay, Marie, Cavallo, Andrea, Di Toro, Giulio
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Publishing Group 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4639853/
https://www.ncbi.nlm.nih.gov/pubmed/26552964
http://dx.doi.org/10.1038/srep16112
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author Spagnuolo, Elena
Plümper, Oliver
Violay, Marie
Cavallo, Andrea
Di Toro, Giulio
author_facet Spagnuolo, Elena
Plümper, Oliver
Violay, Marie
Cavallo, Andrea
Di Toro, Giulio
author_sort Spagnuolo, Elena
collection PubMed
description Rupture fronts can cause fault displacement, reaching speeds up to several ms(−1) within a few milliseconds, at any distance away from the earthquake nucleation area. In the case of silicate-bearing rocks the abrupt slip acceleration results in melting at asperity contacts causing a large reduction in fault frictional strength (i.e., flash weakening). Flash weakening is also observed in experiments performed in carbonate-bearing rocks but evidence for melting is lacking. To unravel the micro-physical mechanisms associated with flash weakening in carbonates, experiments were conducted on pre-cut Carrara marble cylinders using a rotary shear apparatus at conditions relevant to earthquakes propagation. In the first 5 mm of slip the shear stress was reduced up to 30% and CO(2) was released. Focused ion beam, scanning and transmission electron microscopy investigations of the slipping zones reveal the presence of calcite nanograins and amorphous carbon. We interpret the CO(2) release, the formation of nanograins and amorphous carbon to be the result of a shock-like stress release associated with the migration of fast-moving dislocations. Amorphous carbon, given its low friction coefficient, is responsible for flash weakening and promotes the propagation of the seismic rupture in carbonate-bearing fault patches.
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spelling pubmed-46398532015-11-16 Fast-moving dislocations trigger flash weakening in carbonate-bearing faults during earthquakes Spagnuolo, Elena Plümper, Oliver Violay, Marie Cavallo, Andrea Di Toro, Giulio Sci Rep Article Rupture fronts can cause fault displacement, reaching speeds up to several ms(−1) within a few milliseconds, at any distance away from the earthquake nucleation area. In the case of silicate-bearing rocks the abrupt slip acceleration results in melting at asperity contacts causing a large reduction in fault frictional strength (i.e., flash weakening). Flash weakening is also observed in experiments performed in carbonate-bearing rocks but evidence for melting is lacking. To unravel the micro-physical mechanisms associated with flash weakening in carbonates, experiments were conducted on pre-cut Carrara marble cylinders using a rotary shear apparatus at conditions relevant to earthquakes propagation. In the first 5 mm of slip the shear stress was reduced up to 30% and CO(2) was released. Focused ion beam, scanning and transmission electron microscopy investigations of the slipping zones reveal the presence of calcite nanograins and amorphous carbon. We interpret the CO(2) release, the formation of nanograins and amorphous carbon to be the result of a shock-like stress release associated with the migration of fast-moving dislocations. Amorphous carbon, given its low friction coefficient, is responsible for flash weakening and promotes the propagation of the seismic rupture in carbonate-bearing fault patches. Nature Publishing Group 2015-11-10 /pmc/articles/PMC4639853/ /pubmed/26552964 http://dx.doi.org/10.1038/srep16112 Text en Copyright © 2015, Macmillan Publishers Limited http://creativecommons.org/licenses/by/4.0/ This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
spellingShingle Article
Spagnuolo, Elena
Plümper, Oliver
Violay, Marie
Cavallo, Andrea
Di Toro, Giulio
Fast-moving dislocations trigger flash weakening in carbonate-bearing faults during earthquakes
title Fast-moving dislocations trigger flash weakening in carbonate-bearing faults during earthquakes
title_full Fast-moving dislocations trigger flash weakening in carbonate-bearing faults during earthquakes
title_fullStr Fast-moving dislocations trigger flash weakening in carbonate-bearing faults during earthquakes
title_full_unstemmed Fast-moving dislocations trigger flash weakening in carbonate-bearing faults during earthquakes
title_short Fast-moving dislocations trigger flash weakening in carbonate-bearing faults during earthquakes
title_sort fast-moving dislocations trigger flash weakening in carbonate-bearing faults during earthquakes
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4639853/
https://www.ncbi.nlm.nih.gov/pubmed/26552964
http://dx.doi.org/10.1038/srep16112
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