Group B, Poster #254, San Andreas Fault System (SAFS)
Updated frictional behavior of San Andreas Fault gouges from plate-rate friction experiments
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Poster Presentation
2022 SCEC Annual Meeting, Poster #254, SCEC Contribution #12249 VIEW PDF
y weak and velocity-strengthening smectite or smectite-bearing mixed-layer clay minerals.
Using a recent capability to conduct laboratory friction experiments at very slow, plate-rate driving velocities, I extend the friction data for San Andreas Fault gouges for slip rates as low as 2.5 cm/yr. Preliminary data show that a sample of the serpentine block from the Southwest Deforming Zone (G27) shows Byerlee friction values and velocity weakening at low driving velocities with a tendency for approximately velocity-neutral friction at higher rates, broadly consistent with previous work. A sample of the smectite-rich fault core from the Central Deforming Zone (G43) shows a friction coefficient of near 0.4 at the plate-rate of 2.5 cm/yr, as well as large velocity-weakening at slow driving velocities. These observations contrast with previous friction experiments at conventional sliding velocities and geophysical observations, but can be explained by a previously observed time-dependent mechanism where frictional healing and thus fault locking potential become large at long timescales, thus becoming important at very slow sliding velocities. These new results may re-open a discussion on the geomechanics and earthquake potential of the central San Andreas Fault.
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Using a recent capability to conduct laboratory friction experiments at very slow, plate-rate driving velocities, I extend the friction data for San Andreas Fault gouges for slip rates as low as 2.5 cm/yr. Preliminary data show that a sample of the serpentine block from the Southwest Deforming Zone (G27) shows Byerlee friction values and velocity weakening at low driving velocities with a tendency for approximately velocity-neutral friction at higher rates, broadly consistent with previous work. A sample of the smectite-rich fault core from the Central Deforming Zone (G43) shows a friction coefficient of near 0.4 at the plate-rate of 2.5 cm/yr, as well as large velocity-weakening at slow driving velocities. These observations contrast with previous friction experiments at conventional sliding velocities and geophysical observations, but can be explained by a previously observed time-dependent mechanism where frictional healing and thus fault locking potential become large at long timescales, thus becoming important at very slow sliding velocities. These new results may re-open a discussion on the geomechanics and earthquake potential of the central San Andreas Fault.
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Citation: Ikari, M. (2022, 09). Updated frictional behavior of San Andreas Fault gouges from plate-rate friction experiments. Poster Presentation at 2022 SCEC Annual Meeting.
Keywords: San Andreas Fault, SAFOD, friction, velocity weakening
Relevant SCEC Themes:
Stress and Deformation Over Time
