Next Article in Journal
A Novel Approach to Quantitatively Assess the Uniformity of Binary Colloidal Crystal Assemblies
Next Article in Special Issue
Strategies to Approach Stabilized Plasticity in Metals with Diminutive Volume: A Brief Review
Previous Article in Journal
Soda Cans Metamaterial: A Subwavelength-Scaled Phononic Crystal
Previous Article in Special Issue
Dislocation Nucleation on Grain Boundaries: Low Angle Twist and Asymmetric Tilt Boundaries
Article Menu

Export Article

Open AccessFeature PaperReview
Crystals 2016, 6(7), 83; doi:10.3390/cryst6070083

Dislocation Motion and the Microphysics of Flash Heating and Weakening of Faults during Earthquakes

1
Sezione di Sismologia e Tettonofisica, Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Roma, Italy
2
Department of Earth Sciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands
3
LEMR, ENAC, École polytechnique fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
4
Dipartimento di Geoscienze, Università di Padova, Via G. Gradenigo 6, 35131 Padova, Italy
5
School of Earth, Atmospheric and Environmental Sciences, Manchester University, Oxford Street, M13 9PL Manchester, UK
*
Author to whom correspondence should be addressed.
Academic Editor: Ronald W. Armstrong
Received: 5 July 2016 / Revised: 14 July 2016 / Accepted: 16 July 2016 / Published: 22 July 2016
(This article belongs to the Special Issue Crystal Dislocations)
View Full-Text   |   Download PDF [2286 KB, uploaded 25 July 2016]   |  

Abstract

Earthquakes are the result of slip along faults and are due to the decrease of rock frictional strength (dynamic weakening) with increasing slip and slip rate. Friction experiments simulating the abrupt accelerations (>>10 m/s2), slip rates (~1 m/s), and normal stresses (>>10 MPa) expected at the passage of the earthquake rupture along the front of fault patches, measured large fault dynamic weakening for slip rates larger than a critical velocity of 0.01–0.1 m/s. The dynamic weakening corresponds to a decrease of the friction coefficient (defined as the ratio of shear stress vs. normal stress) up to 40%–50% after few millimetres of slip (flash weakening), almost independently of rock type. The microstructural evolution of the sliding interfaces with slip may yield hints on the microphysical processes responsible for flash weakening. At the microscopic scale, the frictional strength results from the interaction of micro- to nano-scale surface irregularities (asperities) which deform during fault sliding. During flash weakening, the visco-plastic and brittle work on the asperities results in abrupt frictional heating (flash heating) and grain size reduction associated with mechano-chemical reactions (e.g., decarbonation in CO2-bearing minerals such as calcite and dolomite; dehydration in water-bearing minerals such as clays, serpentine, etc.) and phase transitions (e.g., flash melting in silicate-bearing rocks). However, flash weakening is also associated with grain size reduction down to the nanoscale. Using focused ion beam scanning and transmission electron microscopy, we studied the micro-physical mechanisms associated with flash heating and nanograin formation in carbonate-bearing fault rocks. Experiments were conducted on pre-cut Carrara marble (99.9% calcite) cylinders using a rotary shear apparatus at conditions relevant to seismic rupture propagation. Flash heating and weakening in calcite-bearing rocks is associated with a shock-like stress release due to the migration of fast-moving dislocations and the conversion of their kinetic energy into heat. From a review of the current natural and experimental observations we speculate that this mechanism tested for calcite-bearing rocks, is a general mechanism operating during flash weakening (e.g., also precursory to flash melting in the case of silicate-bearing rocks) for all fault rock types undergoing fast slip acceleration due to the passage of the seismic rupture front. View Full-Text
Keywords: earthquake mechanics; high speed rock deformation; dislocations; weakening mechanisms; calcite earthquake mechanics; high speed rock deformation; dislocations; weakening mechanisms; calcite
Figures

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

Scifeed alert for new publications

Never miss any articles matching your research from any publisher
  • Get alerts for new papers matching your research
  • Find out the new papers from selected authors
  • Updated daily for 49'000+ journals and 6000+ publishers
  • Define your Scifeed now

SciFeed Share & Cite This Article

MDPI and ACS Style

Spagnuolo, E.; Plümper, O.; Violay, M.; Cavallo, A.; Di Toro, G. Dislocation Motion and the Microphysics of Flash Heating and Weakening of Faults during Earthquakes. Crystals 2016, 6, 83.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Crystals EISSN 2073-4352 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top