An empirically based steady state friction law and implications for fault stability

Area of Science:

• Geophysics
• Rock Mechanics
• Seismology

Background:

• Rate-and-state friction laws (RSFLs) model fault behavior but were derived from low slip rates.
• Extrapolation of RSFLs to seismic slip rates is questionable due to observed dynamic weakening and lubrication effects.

Purpose of the Study:

• To propose a modified rate-and-state friction law (MFL) applicable across a wide range of slip rates.
• To re-evaluate fault stability and seismic rupture processes based on the new MFL.

Main Methods:

• Reviewed a comprehensive dataset of published and unpublished rock friction experiments.
• Developed a modified rate-and-state friction law (MFL) valid from subseismic to seismic slip rates.

Main Results:

• The MFL accurately describes friction at steady-state conditions for slip rates from 0.1 µm/s to 3 m/s.
• Identified a significant velocity weakening initiation between 1-20 cm/s, leading to increased stiffness and potential instability.
• The MFL provides a new framework for understanding fault frictional stability.

Conclusions:

• The modified RSFL is valid across a broad spectrum of slip rates, including seismic conditions.
• The findings have significant implications for understanding earthquake nucleation, propagation, and arrest.
• This work redefines fault stability and offers new insights into seismic event styles.