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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  26 Aug 2020

26 Aug 2020

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This preprint is currently under review for the journal SE.

Effect of normal stress on the friction of brucite: Application to slow earthquake in the mantle wedge

Hanaya Okuda1,2, Ikuo Katayama3, Hiroshi Sakuma4, and Kenji Kawai1 Hanaya Okuda et al.
  • 1Department of Earth and Planetary Science, School of Science, University of Tokyo, Bunkyo, 113-0033 Tokyo, Japan
  • 2Department of Ocean Floor Geoscience, Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, 277-8564 Chiba, Japan
  • 3Department of Earth and Planetary Systems Science, Hiroshima University, Higashi-Hiroshima, 739-8526 Hiroshima, Japan
  • 4Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, 305-0044 Ibaraki, Japan

Abstract. We report the results of friction experiments on brucite under both dry and water-saturated (wet) conditions under various normal stresses (10–60 MPa). The steady-state friction coefficients of brucite were determined to be 0.40 and 0.26 for the dry and wet cases, respectively, independent of the normal stress. Under dry conditions, velocity-weakening behavior was observed in all experiments at various normal stresses. Under wet conditions, velocity weakening was observed at low normal stress (10 and 20 MPa), whereas velocity strengthening was determined at a higher applied normal stress. The microstructural observations on recovered experimental samples indicate localized deformation within the narrow shear band, implying that a small volume of brucite can control the bulk strength in an ultramafic setting and significantly change the frictional properties. Brucite is found to be the only mineral that has a low friction coefficient and exhibits unstable frictional behavior under hydrated mantle wedge conditions, explaining the occurrence of slow earthquakes in the mantle wedge.

Hanaya Okuda et al.

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Hanaya Okuda et al.

Hanaya Okuda et al.


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Latest update: 20 Sep 2020
Publications Copernicus
Short summary
Serpentinite, generated by the hydration of ultramafic rocks, is thought to be related to slow earthquakes in the mantle wedge, although its mechanism is not fully understood yet. We conducted friction experiments on brucite, one of the main minerals of serpentinite, and found that brucite exhibits low and unstable friction under the low effective normal stress condition. This result suggests that brucite can be a key for slow earthquakes in the hydrated mantle wedge.
Serpentinite, generated by the hydration of ultramafic rocks, is thought to be related to slow...