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Evolution of the real area of contact at the laboratory scale during fully dynamic seismic cycles

Baoning Wu, & Sylvain D. Barbot

Submitted September 11, 2022, SCEC Contribution #12485, 2022 SCEC Annual Meeting Poster #162

Empirical rate- and state-dependent friction laws explain many observations of the seismic cycle in the laboratory and in nature. However, the underlying physics is still vibrantly debated. Some physical models explain the strength of frictional resistance by the evolution of the real area of contact on a rough interface, but the relationship between the cycle of contact rejuvenation and aging and fault dynamics remains poorly understood. Laboratory earthquakes at the interface of transparent materials provide a key opportunity to test constitutive models of fault friction. Here, we describe numerical models that resolve all phases of the seismic cycle, including the radiation of seismic waves, to explain the evolution of the real area of contact, before, during, and after the propagation of slow and fast laboratory ruptures. We consider the laboratory observation of the evolving real area of contact along a 5 mm x 200 mm PMMA fracture loaded quasi-statically under 5.5 MPa normal stress (Svetlizky, Bayard, and Fineberg, 2019). The model reproduces the 40% drop in real area of contact associated with the passage of sub-Rayleigh rupture fronts. The successful comparison of simulated and laboratory data imply valid constitutive relationships between the real area of contact, and the size and age of micro-asperities at contact junctions. In particular, the state variable of rate- and state-dependent friction is directly related to an observable quantity in the laboratory.

Wu, B., & Barbot, S. D. (2022, 09). Evolution of the real area of contact at the laboratory scale during fully dynamic seismic cycles. Poster Presentation at 2022 SCEC Annual Meeting.

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