Dynamic Friction Modeling
Earthquake nucleation and rupture occur through a combination of spatially heterogeneous elastodynamic stresses and temporally dynamic friction evolution on the fault interface. We are exploring models that implement experimentally-motivated friction properties to determine the ability of these relative effects to explain observed behaviors, such as seismic cycles, population statistics, and aseismic pre-slip nucleation of large earthquakes.
Earthquakes are modeled with simplified friction laws, usually either based on low-velocity, step change measurements or direct parameterizations that are limited in how they can be applied beyond specific lab conditions. Recent experiments that drive fault slip as we expect occurs during an earthquake (with dramatic acceleration and deceleration never reaching steady-state) show complex changes in friction over time that commonly-used models do not represent. Introducing models developed by engineers to predict friction in robotics, called 'bristle-state' from the idea that bristle asperities bend before fully slipping, we show how different mathematical forms are able to reproduce the frictional evolution from realistic earthquake slip experiments. These models are specially designed to capture the ‘breakaway’ friction force during the initiation of full sliding, and can be driven arbitrarily, offering the opportunity to better represent friction during nucleation and transients far from steady-state (Saltiel et al., Frontiers 2020).
Utilizing data-driven, 'physics-aware', machine learning algorithms, we are better constraining a universal friction law to fit a wide range of experimental rock friction data. Building on common rate-state friction formulations, and integrated friction approach from bristle-state friction models, this study will quantitatively determine what mathematical terms are needed.
Collaborators: Tushar Mittal (MIT); Jorge Crempien & Patrico Venegas-Aravena (Pontifica Universidad Católica de Chile); Jaime Campos (Universidad de Chile)