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Title: Experimental evidence for dynamic friction on rock fractures from frequency-dependent nonlinear hysteresis and harmonic generation: Low-Frequency Torsional Dynamic Friction

Frictional properties affect the propagation of high-amplitude seismic waves across rock fractures and faults. Laboratory evidence suggests that these properties can be measured in active seismic surveys, potentially offering a route to characterizing friction in situ. Here, we present experimental results from a subresonance torsional modulus and attenuation apparatus that utilizes micron-scale sinusoidal oscillations to probe the nonlinear stress-strain relation at a range of strain amplitudes and rates. Nonlinear effects are further quantified using harmonic distortion; however, time series data best illuminate underlying physical processes. The low-frequency stress-strain hysteretic loops show stiffening at the sinusoid's static ends, but stiffening is reduced above a threshold frequency. This shape is determined by harmonic generation in the strain; the stress signal has no harmonics, confirming that the fractured sample is the source of the nonlinearity. These qualitative observations suggest the presence of rate-dependent friction and are consistent between fractures in three different rock types. We propose that static friction at the low strain rate part of the cycle, when given sufficient “healing” time at low oscillation frequencies, causes this stiffening cusp shape in the hysteresis loop. While rate-and-state friction is commonly used to represent dynamic friction, it cannot capture static friction or negativemore » slip velocities. So we implement another dynamic friction model, based on the work of Dahl, which describes this process and produces similar results. Since the two models have a similar form, parameterizations of field data could constraint fault model inputs, such as specific location velocity strengthening or weakening properties.« less
Authors:
ORCiD logo [1] ;  [2] ; ORCiD logo [3] ; ORCiD logo [3] ;  [2]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth and Environmental Sciences Area; Univ. of California, Berkeley, CA (United States). Earth and Planetary Science Dept.
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth and Environmental Sciences Area
  3. Univ. of California, Berkeley, CA (United States). Earth and Planetary Science Dept.
Publication Date:
Grant/Contract Number:
AC02-05CH11231; FC26-05NT42587
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Solid Earth
Additional Journal Information:
Journal Volume: 122; Journal Issue: 7; Journal ID: ISSN 2169-9313
Publisher:
American Geophysical Union
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Fossil Energy (FE)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; dynamic friction; seismic frequency; fractures; nonlinear elasticity; harmonic generation; hysteresis
OSTI Identifier:
1476511
Alternate Identifier(s):
OSTI ID: 1375067

Saltiel, Seth, Bonner, Brian P., Mittal, Tushar, Delbridge, Brent, and Ajo-Franklin, Jonathan B.. Experimental evidence for dynamic friction on rock fractures from frequency-dependent nonlinear hysteresis and harmonic generation: Low-Frequency Torsional Dynamic Friction. United States: N. p., Web. doi:10.1002/2017JB014219.
Saltiel, Seth, Bonner, Brian P., Mittal, Tushar, Delbridge, Brent, & Ajo-Franklin, Jonathan B.. Experimental evidence for dynamic friction on rock fractures from frequency-dependent nonlinear hysteresis and harmonic generation: Low-Frequency Torsional Dynamic Friction. United States. doi:10.1002/2017JB014219.
Saltiel, Seth, Bonner, Brian P., Mittal, Tushar, Delbridge, Brent, and Ajo-Franklin, Jonathan B.. 2017. "Experimental evidence for dynamic friction on rock fractures from frequency-dependent nonlinear hysteresis and harmonic generation: Low-Frequency Torsional Dynamic Friction". United States. doi:10.1002/2017JB014219. https://www.osti.gov/servlets/purl/1476511.
@article{osti_1476511,
title = {Experimental evidence for dynamic friction on rock fractures from frequency-dependent nonlinear hysteresis and harmonic generation: Low-Frequency Torsional Dynamic Friction},
author = {Saltiel, Seth and Bonner, Brian P. and Mittal, Tushar and Delbridge, Brent and Ajo-Franklin, Jonathan B.},
abstractNote = {Frictional properties affect the propagation of high-amplitude seismic waves across rock fractures and faults. Laboratory evidence suggests that these properties can be measured in active seismic surveys, potentially offering a route to characterizing friction in situ. Here, we present experimental results from a subresonance torsional modulus and attenuation apparatus that utilizes micron-scale sinusoidal oscillations to probe the nonlinear stress-strain relation at a range of strain amplitudes and rates. Nonlinear effects are further quantified using harmonic distortion; however, time series data best illuminate underlying physical processes. The low-frequency stress-strain hysteretic loops show stiffening at the sinusoid's static ends, but stiffening is reduced above a threshold frequency. This shape is determined by harmonic generation in the strain; the stress signal has no harmonics, confirming that the fractured sample is the source of the nonlinearity. These qualitative observations suggest the presence of rate-dependent friction and are consistent between fractures in three different rock types. We propose that static friction at the low strain rate part of the cycle, when given sufficient “healing” time at low oscillation frequencies, causes this stiffening cusp shape in the hysteresis loop. While rate-and-state friction is commonly used to represent dynamic friction, it cannot capture static friction or negative slip velocities. So we implement another dynamic friction model, based on the work of Dahl, which describes this process and produces similar results. Since the two models have a similar form, parameterizations of field data could constraint fault model inputs, such as specific location velocity strengthening or weakening properties.},
doi = {10.1002/2017JB014219},
journal = {Journal of Geophysical Research. Solid Earth},
number = 7,
volume = 122,
place = {United States},
year = {2017},
month = {6}
}