Measuring Rate‐ and State‐Dependent Stick‐Slip Friction Parameters Under a Low‐Stiffness Loading Condition

ABSTRACT The rate‑ and state‑dependent friction (RSF) law effectively characterizes fault stick‑slip behavior, with its parameters acting as key variables controlling the mechanical response of fault surfaces. Because these parameters are highly sensitive to the stiffness of the measuring system, this study investigates a method for determining RSF parameters under low‑stiffness loading. Numerical simulations are used to analyze the relationship between characteristic features of the low‑stiffness stress–displacement curves and the friction parameters, thereby verifying the feasibility of the approach. Comparisons further reveal distinct measurement behaviors between high‑ and low‑stiffness systems. The results demonstrate that friction parameters can be reliably inverted from shear tests using a low‑stiffness machine. This method substantially reduces apparatus requirements and enables parameter extraction from the system's spontaneous stick‑slip response without an imposed velocity step, opening the possibility for continuous, real‑time monitoring of friction evolution during loading.