Abstract
For millennia, human‐made machinery incorporated rolls and wheels to reduce frictional resistance, yet similar elements are practically absent in natural systems. We found in rock shear experiments that tiny, cylindrical rolls composed of nanoparticulate gouge spontaneously develop along experimental faults and lead to drastic dynamic weakening. The experiments were conducted on granite samples with a rotary apparatus at slip velocity range of 0.001–1 m/s and normal stress up to 14.4 MPa. At moderate slip velocities of <0.1 m/s, the fault slip localized along flakes of highly smooth surfaces that frequently displayed a multitude of cylindrical rolls. Roll diameters are ~1 µm, their length range is 2–20 µm, and they are made of tightly‐packed ultrafine (20–50 nm) powder grains. These rolls are systematically oriented normal to the slip direction. The presence of rolls corre-lates well with reduction of the macroscopic friction. We propose that development of powder rolls on fault principal slip zone surfaces leads to a transition from sliding‐dominated slip to rolling‐dominated slip, thus serving as an effective mechanism of fault weakening.
Original language | English |
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Title of host publication | Geophysical Monograph Series |
Publisher | John Wiley and Sons Inc. |
Pages | 133-150 |
Number of pages | 18 |
DOIs | |
State | Published - 2017 |
Externally published | Yes |
Publication series
Name | Geophysical Monograph Series |
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Volume | 227 |
ISSN (Print) | 0065-8448 |
ISSN (Electronic) | 2328-8779 |
Bibliographical note
Publisher Copyright:© 2017 American Geophysical Union. Published 2017 by John Wiley & Sons, Inc.