The Influence of Roughness on Experimental Fault Mechanical Behavior and Associated Microseismicity

Area of Science:

• Geophysics
• Earth Sciences
• Seismology

Background:

• Fault surface roughness influences seismic behavior.
• Previous experimental studies often used low slip velocities, limiting understanding of earthquake nucleation and propagation.

Purpose of the Study:

• Investigate the effect of varying fault surface roughness on earthquake nucleation and runaway slip.
• Analyze microseismicity and slip behavior under different roughness conditions.

Main Methods:

• Performed dry load-stepping biaxial experiments on bare rock surfaces with diverse roughness.
• Recorded and localized acoustic emissions during deformation.
• Achieved slip velocities up to 100 mm/s.

Main Results:

• Smoother surfaces exhibited more frequent slip instabilities, larger stress drops, and higher slip velocities compared to rougher faults.
• Smoother samples showed a higher proportion of large-magnitude acoustic emission events (higher Gutenberg-Richter b-value).
• Cumulative seismic moment was comparable across all roughness conditions.

Conclusions:

• Local surface topography heterogeneity influences macroscopic frictional stability and microseismicity.
• Fault roughness can create stress barriers that halt rupture, a phenomenon previously demonstrated numerically.