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Flash weakening of serpentinite at near-seismic slip rates

Flash weakening of serpentinite at near-seismic slip rates,10.1029/2010JB007833,Journal of Geophysical Research,Arjun H. Kohli,David L. Goldsby,Greg H

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Flash weakening of serpentinite at near-seismic slip rates   (Citations: 1)
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To investigate the processes responsible for dynamic frictional weakening in antigorite serpentinite, we conducted single-velocity and velocity-stepping friction experiments at slip rates (V) from 0.01 to 0.4 m s−1, sliding displacements up to 40 mm, and a normal stress of 5 MPa. Single-velocity experiments demonstrate an approximately 1/V dependence of friction on velocity above a characteristic weakening velocity Vw ≈ 0.1 m s−1, consistent with theoretical predictions for flash heating and subsequent weakening of asperities. Velocity-stepping experiments impose stepwise increases in slip rate show stepwise weakening at slip rates above Vw. Scanning electron microscopy of experimental fault surfaces reveals nanoparticle gouge textures at raised sites (∼10 μm in diameter) in tests that exhibit dramatic weakening. Furthermore, X-ray diffraction analyses of fault gouge from the sliding surface document the formation of significant talc in these tests, indicating that weakening temperatures reached 500°C–700°C. In contrast, no talc is observed in samples for which V remained significantly below Vw. The observed value for Vw is consistent with published microphysical models for flash weakening when independent constraints on the thermal stability and contact strength of antigorite are considered. Finally, while serpentinite displays velocity-strengthening behavior at plate tectonic slip rates, our results indicate that seismic ruptures propagating into serpentinized regions in the shallow lithosphere may trigger seismicity or slow earthquakes, after limited amounts of displacement.
Journal: Journal of Geophysical Research , vol. 116, no. B3, 2011
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    • ...Thermal pore fluid pressurization [Sibson, 1973; Lachenbruch, 1980] may lead to significant weakening during shear of low‐permeability rock or wet gouge [Han et al., 2010; Ferri et al., 2010; Ujiie and Tsutsumi, 2010], and flash heating at asperity contacts [Rice, 2006] is consistent with some experimental data and microstructural observations [Brantut et al., 2008; Beeler et al., 2008; Kohli et al., 2011]...

    Hiroko Kitajima, et al. Dynamic weakening of gouge layers in high-speed shear experiments: Ass...

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