Frictional Mechanics in Seismic Faulting

Frictional mechanics in seismic faulting underpin the processes by which stress accumulates and is released during earthquakes. At its core, fault motion is governed by the interplay between shear stress, normal stress and the evolving properties of the contact surfaces. Laboratory and field studies reveal that frictional resistance is not constant but depends on slip velocity, contact history and the presence of fluids. These factors determine whether a fault segment will slip stably or rupture catastrophically. Rate-and-state friction laws capture the influence of slip rate and interfacial state on resistance, while concepts such as fracture energy describe the partitioning of strain energy into heat, new surface creation and radiated waves. Heterogeneity in fault zone composition, roughness and fluid pressure leads to spatial and temporal variations in strength, giving rise to phenomena as diverse as slow-slip transients, afterslip and dynamic rupture. Understanding these processes across scales—from molecular motions in adsorbed films to kilometre-long ruptures—is essential to improve models of earthquake nucleation, propagation and hazard assessment.

Research from Nature Portfolio

Recent experimental work has combined data-driven methods with fundamental physics by embedding frictional laws within neural network architectures. Physics-informed neural networks trained on ultrasonic fault zone observations have demonstrated enhanced prediction of laboratory earthquakes, outperforming purely statistical models and offering insights into the physical variables essential for failure forecasting. These models show promise for scaling to natural faults by encoding constitutive laws directly into the learning process. In parallel, friction experiments on laterally heterogeneous fault gouges have revealed that spatial juxtaposition of strong and weak materials dramatically reduces overall fault strength and stability. Heterogeneous patches of clay and quartz gouge undergo differential compaction and shear localisation, producing stress concentrations that promote unstable slip. These findings underscore the importance of geological heterogeneity in controlling the transition between slow-slip events and dynamic rupture on active faults.

Frictional Mechanics in Seismic Faulting publication trend

The graph below shows the total number of articles in frictional mechanics in seismic faulting across all publications each year (not limited to Nature Index journals).

Technical terms

Rate-and-state friction: Model describing frictional resistance as a function of slip rate and the evolving state of contact asperities.

Fault gouge: Granular material within the fault zone produced by rock comminution during slip.

Asperity: Roughness protrusion on a fault surface that supports local contact and frictional strength.

Fracture energy (breakdown work): Energy dissipated during rupture propagation and slip on a fault, scaling with coseismic displacement.

Velocity weakening/strengthening: Behaviour in which friction decreases/increases with rising slip velocity, governing slip stability.

Physics-informed neural network (PINN): Computational model integrating governing physical laws into neural network training to enhance predictive capability.

References

1. Using a physics-informed neural network and fault zone acoustic monitoring to predict lab earthquakes. Nature Communications (2023).
2. Fault rock heterogeneity can produce fault weakness and reduce fault stability. Nature Communications (2022).
3. From Molecular to Multiasperity Contacts: How Roughness Bridges the Friction Scale Gap. ACS Nano (2023).
4. Fracture Energy and Breakdown Work During Earthquakes. Annual Review of Earth and Planetary Sciences (2023).