Fault Friction Dynamics: A New Perspective

For many years, scientists studying earthquakes believed that the friction of rocks along fault lines was directly tied to temperature. A recent study led by USC, published in the Proceedings of the National Academy of Sciences, challenges this long-held assumption. The findings suggest that various mechanisms influence the frictional resistance of faults, questioning established views on seismic activity.

Sylvain Barbot, an associate professor at USC Dornsife, explained that the traditional view held that fault friction changes steadily with temperature. His research indicates that friction is largely independent of temperature until a rock transitions from a brittle to a semi-brittle state, where temperature effects become significant.

The study analyzed data from experiments on different rock types, including granite, basalt, and olivine, under conditions simulating deep Earth environments. Barbot found that this transition from brittle to semi-brittle is crucial for understanding rock mechanics and geological processes.

In a brittle state, rocks fracture and break, while in a semi-brittle state, they exhibit a mix of brittle and ductile behavior, allowing them to permanently deform under stress. Barbot emphasized that this transition leads to sudden changes in rock friction that traditional models do not account for, indicating a need to rethink fundamental concepts of fault mechanics.

The "direct effect of friction" refers to immediate changes in friction due to rapid variations in sliding velocity between two surfaces on a fault. Most existing theories suggest this friction is continuously affected by temperature. Barbot’s study challenges this reliance on thermal activation, suggesting that predictive models for fault friction need revision to improve earthquake forecasts.

The next phase of the research aims to refine the understanding of fault friction dynamics. Barbot noted that incorporating these findings into physics-based models of the seismic cycle could significantly enhance the accuracy and reliability of earthquake hazard assessments and long-term predictions.

Overall, this research not only sheds light on the complexities of rock friction but also paves the way for better predictions of seismic activity, ultimately contributing to safer and more informed approaches to earthquake preparedness.