TY - JOUR
T1 - Slide-Hold-Slide Protocols and Frictional Healing in Discrete Element Method (DEM) Simulations of Granular Fault Gouge
AU - Ferdowsi, Behrooz
AU - Rubin, Allan M.
N1 - Funding Information:
BF acknowledges support from the Department of Geosciences, Princeton University, in form of a Harry H. Hess postdoctoral fellowship. Research was sponsored by the US National Science Foundation (NSF) awards EAR‐1547286 and EAR‐1946434, by the US Geological Survey (USGS), Department of the Interior, awards G19AP00048 and G20AP00112, and by the US Army Research Office (ARO) award W911NF‐20‐1‐0154, all of the awards to AMR. The authors thank Pathikrit Bhattacharya, Terry E. Tullis, Nicholas M. Beeler, and Keishi Okazaki, for their permission to use the data shown in Figure 2d of this manuscript. Parallel programs were run on computers provided by the Princeton Institute for Computational Science and Engineering (PICSciE). The 3‐D visualizations of the model were performed using the open‐source visualization software “The Persistence of Vision Raytracer” POV‐Ray ( http://www.povray.org ). Most of the data analysis were carried out using the open‐source Python library, NumPy ( https://numpy.org ). The 2‐D plots were made with the Python library Matplotlib ( www.matplotlib.org ). The authors wish to thank reviewers Jianye Chen and Norm Sleep for their reviews and suggestions which helped improve and clarify this manuscript. The Associate Editor also provided comments. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government.
Funding Information:
BF acknowledges support from the Department of Geosciences, Princeton University, in form of a Harry H. Hess postdoctoral fellowship. Research was sponsored by the US National Science Foundation (NSF) awards EAR-1547286 and EAR-1946434, by the US Geological Survey (USGS), Department of the Interior, awards G19AP00048 and G20AP00112, and by the US Army Research Office (ARO) award W911NF-20-1-0154, all of the awards to AMR. The authors thank Pathikrit Bhattacharya, Terry E. Tullis, Nicholas M. Beeler, and Keishi Okazaki, for their permission to use the data shown in Figure?2d of this manuscript. Parallel programs were run on computers provided by the Princeton Institute for Computational Science and Engineering (PICSciE). The 3-D visualizations of the model were performed using the open-source visualization software ?The Persistence of Vision Raytracer? POV-Ray (http://www.povray.org). Most of the data analysis were carried out using the open-source Python library, NumPy (https://numpy.org). The 2-D plots were made with the Python library Matplotlib (www.matplotlib.org). The authors wish to thank reviewers Jianye Chen and Norm Sleep for their reviews and suggestions which helped improve and clarify this manuscript. The Associate Editor also provided comments. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government.
Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.
PY - 2021/12
Y1 - 2021/12
N2 - 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 & 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 (SH) protocols. A few slide-hold-slide (SHS) 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 Discrete Element Method (DEM) model in SH and SHS protocols over a wide range of sliding velocities, hold durations, and system stiffnesses, and provide additional support for this view. We find that, similar to laboratory data, the rate of stress decay during SH 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 following long hold times, the model, similar to lab data, produces a nearly constant rate of frictional healing with log hold time, with that rate being in the range of ∼0.5 to 1 times the RSF “state evolution” parameter b. 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 state evolution under the Aging law, even though the associated stress decay is similar to that predicted by the Slip and not the Aging law.
AB - 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 & 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 (SH) protocols. A few slide-hold-slide (SHS) 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 Discrete Element Method (DEM) model in SH and SHS protocols over a wide range of sliding velocities, hold durations, and system stiffnesses, and provide additional support for this view. We find that, similar to laboratory data, the rate of stress decay during SH 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 following long hold times, the model, similar to lab data, produces a nearly constant rate of frictional healing with log hold time, with that rate being in the range of ∼0.5 to 1 times the RSF “state evolution” parameter b. 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 state evolution under the Aging law, even though the associated stress decay is similar to that predicted by the Slip and not the Aging law.
KW - frictional healing
KW - granular friction
KW - granular rheology
KW - rate- and state-dependent friction
KW - rate-and-state Slip law
KW - slide-hold-slide experiments
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U2 - 10.1029/2021JB022125
DO - 10.1029/2021JB022125
M3 - Article
AN - SCOPUS:85121758562
SN - 2169-9313
VL - 126
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
IS - 12
M1 - e2021JB022125
ER -