Poster #144, Fault and Rupture Mechanics (FARM)
Two timescales of fault stabilization by dilatant hardening: slow slip events followed by prolonged dynamic rupture
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Poster Presentation
2020 SCEC Annual Meeting, Poster #144, SCEC Contribution #10709 VIEW PDF
nd Pf fail slowly over 10-100 seconds, followed by minor unstable failure. The observed stabilization is consistent with that expected from the drainage conditions constrained from bulk permeabilities and far-field strain rates. The timescales of failure observed over a range of strain rates show a unique scaling relationship with the timescale of characteristic strain for a given strain rate: tfailure ~ tdef n. Fully unstable failure shows n ~ 1, while stabilized failure exhibits n ~ 0.07, smaller than n ~ 1/3 predicted from theoretical models of dilatant hardening. (2) In addition, stabilization also occurs during the unstable part of failure. 4-6% porosity samples deformed at high Pc and Pf display prolonged unstable failure (~1 second based on 0.1 MHz strain gage data) along with tremor-like seismicity. In contrast, experiments showing fully unstable failure are marked by distinct, <10 millisecond earthquake-like seismicity. The timescales of prolonged unstable failure show little correlation with imposed strain rates. Thus, our results suggest that, for the long-term stabilization, dilatant hardening is governed by bulk fluid diffusion and far-field strain rate, but, for the short-term stabilization, by much shorter timescales of deformation (e.g., dynamic rupture).
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