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Slide-hold-slide experiments and frictional healing in a simulated granular fault gouge
  • Behrooz Ferdowsi,
  • Allan M. Rubin
Behrooz Ferdowsi
Princeton University, Princeton University, Princeton University

Corresponding Author:behrooz@princeton.edu

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Allan M. Rubin
Princeton University, Princeton University, Princeton University
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The empirical constitutive modeling framework of Rate- and State-dependent Friction (RSF) is commonly used to describe the time-dependent frictional response of fault gouge to perturbations from steady sliding. In a previous study (Ferdowsi and Rubin, 2020), we found that a granular-physics-based model of a fault shear zone, with time-independent properties at the contact scale, reproduces the phenomenology of laboratory rock and gouge friction experiments in velocity-step and slide-hold protocols. A few slide-hold-slide simulations further suggested that the granular model might outperform current empirical RSF laws in describing laboratory data. Here, we explore the behavior of the same model in slide-hold and slide-hold-slide protocols over a wide range of sliding velocities, hold durations, and system stiffnesses, and provide additional support for this view. We find that, as is the case for laboratory data, the rate of stress decay during slide-hold simulations is in general agreement with the “Slip law” version of the RSF equations, using parameter values determined independently from velocity step tests. During reslides, the model, similar to lab data, produces a nearly constant rate of frictional healing with log hold time, at long hold times, with that rate being close to the RSF “state evolution” parameter b, consistent with the “Aging law” version of the RSF equations. We also find that, as in laboratory experiments, the granular layer undergoes log-time compaction during holds. This is consistent with the traditional understanding of the Aging law, even though the associated stress decay is similar to that predicted by the Slip and not the Aging law.
Dec 2021Published in Journal of Geophysical Research: Solid Earth volume 126 issue 12. 10.1029/2021JB022125