Journal Article

Velocity and Temperature Dependence of Steady‐State Friction of Natural Gouge Controlled by Competing Healing Mechanisms

Barbot, Sylvain, Nie, Shiying

2024

Overview

The empirical rate‐ and state‐dependent friction law is widely used to explain the frictional resistance of rocks. However, the constitutive parameters vary with temperature and sliding velocity, preventing extrapolation of laboratory results to natural conditions. Here, we explain the frictional properties of natural gouge from the San Andreas Fault, Alpine Fault, and the Nankai Trough from room temperature to ∼300°C for a wide range of slip‐rates with constant constitutive parameters by invoking the competition between two healing mechanisms with different thermodynamic properties. A transition from velocity‐strengthening to velocity‐weakening at steady‐state can be attained either by decreasing the slip‐rate or by increasing temperature. Our study provides a framework to understand the physics underlying the slip‐rate and state dependence of friction and the dependence of frictional properties on ambient physical conditions. Plain Language Summary The physics of friction is crucial to understanding fault mechanics, impacting virtually every aspect of earthquake initiation, propagation, and associated hazards. The mechanics of active fault zones exhibit a complex dependence on temperature and sliding velocity among other factors. The frictional resistance of natural gouge can be explained by empirical rate‐ and state‐dependent friction laws for a limited range of conditions. However, explaining the non‐stationary frictional behavior of gouge friction and extrapolation of laboratory constraints to natural conditions remains challenging. In this study, we describe a constitutive law that predicts the velocity of sliding of natural gouge based on applied shear stress, effective confining pressure, and the ambient temperature of the fault. The transition from stable to unstable sliding is controlled by the competition between micro‐mechanisms of deformation within the gouge that dominate in distinct ranges of temperature and slip‐rate. Once calibrated to mechanical data for a specific lithology and confining pressure, the model explains the temperature and slip‐rate control on fault stability, allowing extrapolation of laboratory data to natural conditions. Key Points The dependence of natural gouge friction on temperature and velocity cannot be captured by empirical laws with constant coefficients The competition of healing mechanisms explains a velocity‐ and temperature‐controlled transition between velocity‐weakening and hardening The constitutive law explains the mechanics of natural gouge from various tectonic settings, allowing scaling up from laboratory to nature

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Ambient temperature / Confining / Deformation / Earthquakes / Extrapolation / Fault lines / Fault zones / Friction / Friction resistance / Geological faults / Healing / Lithology / Mechanics (physics) / Parameters / Physics / Room temperature / Seismic activity / Shear stress / Sliding / Slip / Slumping / Temperature / Temperature dependence / Thermal properties / Thermodynamic properties / Velocity