Microphysical Modeling of Fault Slip and Stability Transition in Hydrothermal Conditions

Abstract

Field and laboratory observations indicate that the frictional behaviors of faults depend on hydrothermal conditions. We extend the microphysical Chen‐Niemeijer‐Spiers (CNS) model to hydrothermal conditions by using the observed temperature variation of indentation hardness to infer the temperature dependence of a microphysical parameter ()atrueμ∼ $\left({a}_{\tilde{\mu }}\right)$. This parameter is assumed constant in previous versions of the CNS model. A simple spring‐slider system is used to simulate the fault system and investigate the steady‐state frictional behaviors of wet granite gouges. Our numerical results quantitatively reproduce experimental data showing the frictional‐plastic transition. The results also describe the transition from velocity‐strengthening at low temperatures (<160°C), to velocity‐weakening at intermediate temperatures (160°C–370°C), then back to velocity‐strengthening at high temperatures (>370°C). In our extended CNS model, these results suggest that the dominant shear deformation mechanism does transition from frictional granular flow to fully plastic creep with increasing temperature.

Velocity Dependence of Rate‐And‐State Friction in Granular Fault Gouge and Implications for Slow‐Slip Events

“…A large $${a}_{\widetilde{\mu }}$$ is able to increase the velocity‐strengthening of friction at high velocity (Figure 7b) and thus SSEs are more expected. The $${a}_{\widetilde{\mu }}$$‐value may vary under different hydrothermal and stress conditions due to its normal stress and temperature dependence (Mei & Rudnicki, 2023a; Mei et al., 2024; Van den Ende et al., 2018). In addition, a small M ‐value can promote the occurrence of SSEs by decreasing the b ‐value (Equation 26) and increasing velocity‐strengthening of friction at high velocities.…”

“…The original CNS model has satisfactorily captured the main features of typical experiments including the “velocity‐stepping” and “slide‐hold‐slide” experiments (Chen et al., 2017, 2020). The extended CNS model can also model seismic slip behaviors (Chen et al., 2021, 2022) and stability transition in hydrothermal conditions (Mei & Rudnicki, 2023a, 2023b; Mei et al., 2024). As applied to natural faults, the original CNS model can be used to interpret various fault slip phenomena, such as earthquake nucleation (Van den Ende et al., 2018), interseismic fault healing (Chen et al., 2020; Hunfeld et al., 2020), as well as SSEs in dilatant and fluid‐saturated faults (Chen, 2023).…”

Micro‐Thermomechanical Modeling of Rocks With Temperature‐Dependent Friction and Damage Laws

“…The stability of deep rocks plays a crucial role in man‐made and natural structures, such as enhanced geothermal systems, shale oil/gas resource extraction, geological disposal of nuclear waste, and fault slippage (Kumari et al., 2019; Mei & Rudnicki, 2023; Nielsen et al., 2021; Zhou et al., 2022). Deep rocks inevitably suffering high geo‐temperature and high geo‐stress, exhibit different mechanical properties from those near the surface and are highly susceptible to hysteretic rockbursts or large creep deformation hazards (Feng et al., 2012; Nara et al., 2013).…”