The effect of contact area distribution on the frictional properties of a modeled fault

Jaiden A. Zak, Will Steinhardt, & Emily E. Brodsky

Submitted September 10, 2023, SCEC Contribution #13261, 2023 SCEC Annual Meeting Poster #114

Frictional strength is controlled by the total real area of contact between surfaces. This fundamental tenet has been in place since the work of Bowden and Tabor and has motivated significant work measuring the topography of fault surfaces with an eye towards understanding friction at various scales. However, the role of the spatial distribution of the real area of contact has been less examined. How does the frictional resistance during slip vary based on the spacing of asperities? Here we examine this question directly through a scaled experiment.

We use a system of asperities cast in silicone attached to a rotary shear device to investigate the role of contact area. The counter surface is a glass plate that is illuminated to allow direct measurement of the real area of contact, which we image with a high-speed camera. Samples were prepared with 8 asperities arranged either in pairs, or spread evenly around the perimeter of the circle. We verified that the real area of contact and average coefficient of friction was the same for both configurations, however the dynamical resistance and rupture behavior of the system were markedly different, with the paired distributions producing a greater variance in friction. In addition, slip events occurring on single asperities were more likely to be correlated with slip events on other asperities for the paired distribution than for the uniform distribution. As a result, the paired samples produced more larger events (events where >4 asperities fail together) and fewer small events (where only 1 or 2 asperities fail). We infer from this work that roughness distribution must be characterized on fault surfaces to predict behavior in addition to the overall amplitude of roughness.

Key Words
Fault Roughness, Asperity Distribution, Friction

Citation
Zak, J. A., Steinhardt, W., & Brodsky, E. E. (2023, 09). The effect of contact area distribution on the frictional properties of a modeled fault. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)