Journal Article

Thermobaric Activation of Fault Friction

Zhang, L., Yang, Z., Zhang, H., Barbot, S., Guvercin, S. E.

2025

Overview

The constitutive behavior of faults intervenes in virtually every aspect of the seismic phenomenon but is poorly understood, particularly regarding how effective normal stress affects the boundaries of the seismogenic zone. Here, we explore the mechanical properties of Pelona schist, Westerly granite, phyllosilicate‐rich gouge, gabbro, hornblende, lawsonite blueschist, montmorillonite, and smectite in hydrothermal conditions at various confining pressures and explain the laboratory observations with a physical model of fault friction. The thermobaric activation of healing and deformation mechanisms explains the boundaries of unstable slip as a function of slip‐rate, temperature, and effective normal stress for a given lithology. The constitutive law affords extrapolation of laboratory data in the conditions relevant to seismic cycles throughout the crust, explaining the focus of large earthquakes in collision, subduction, and continental and oceanic transform settings. Plain Language Summary An important goal of earthquake physics involves predicting the failure of rocks under the various physical conditions encountered during the seismic cycle. Here, we analyze mechanical data for Pelona schist, Westerly granite, phyllosilicate‐rich gouge, gabbro, hornblende, lawsonite blueschist, montmorillonite, and smectite that reveal how normal stress, temperature, and slip‐rate affect the frictional properties of rocks. We capture these effects consistently at constant coefficients with a physics‐based constitutive friction law. The boundaries of the seismogenic zone follow a thermobaric activation, whereby the transition temperature is a function of pressure. Increasing confining pressure may induce or inhibit velocity‐weakening behavior, depending on the constitutive properties controlling the healing and deformation mechanisms. The constitutive model provides an increasingly realistic representation of fault behavior during seismic cycles applicable to a wide range of tectonic contexts. Key Points The temperature boundaries of the seismogenic zone depend on confining pressure, implying a thermobaric activation of fault friction The model explains schist, granite, gabbro, hornblende, clays, and natural gouge friction evolution with velocity, temperature, and pressure The constitutive model provides a realistic representation of fault behavior during seismic cycles applicable to all tectonic contexts

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Boundaries / Confining / constitutive law / Constitutive models / Deformation / Deformation mechanisms / Earthquake prediction / Earthquakes / Fault lines / fault mechanics / Friction / Gabbro / Granite / Healing / Lithology / Mechanical properties / Montmorillonite / Montmorillonites / Normal stress / Physics / Rock properties / Rocks / Schist / Schists / Seismic activity / Seismic response / Slip / Smectites / Subduction / Subduction (geology) / Tectonics / Transition temperature / Transition temperatures