Real area of contact as the state variable in rate-and-state friction

Baoning Wu, & Sylvain D. Barbot

Submitted September 10, 2023, SCEC Contribution #13243, 2023 SCEC Annual Meeting Poster #113

Rate- and state-dependent friction laws are commonly used to explain seismic observations in both laboratory and natural settings. However, the underlying physics of state dependence remains an active area of debate. We present a physical model that links the evolution of the real area of contact on a rough interface to the state variable in the rate-and-state friction law. Our model proposes that the real area of contact changes due to creep or rejuvenation at the micro-contacts, which corresponds to changes in the state variable. To validate our model, we conduct numerical simulations on two laboratory friction experiments at the interface of transparent materials. The first experiment is a classic velocity-step and slide-hold-slide test on ~1cm^2 acrylic plastic conducted by Dieterich and Kilgore (1994), while the second experiment involves the dynamic rupture of laboratory earthquakes along a 5 mm x 200 mm PMMA interface conducted by Svetlizky, Bayard, and Fineberg (2019). Our simulations reproduce the laboratory data reasonably well, suggesting a valid constitutive relationship between the real area of contact and the size and age of micro-asperities at contact junctions. Our findings demonstrate a direct link between the state-variable and an observable quantity in the laboratory, providing new insights into the physical mechanisms underlying rate- and state-dependent friction laws.

Key Words
rate and state friction law; lab experiments

Wu, B., & Barbot, S. D. (2023, 09). Real area of contact as the state variable in rate-and-state friction. Poster Presentation at 2023 SCEC Annual Meeting.

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