Faulting is typically a two timescale process, that is, rapid failure and slow (chemical) healing. Once failed, a rock has a long memory until slow chemical processes have time to re-establish the grain–grain contacts underlying rock competency. The memory of rock failure can be captured by a sufficiently rich textural model, and the texture must be coevolved with rock stress and deformation to yield a self-consistent model of strain hardening/weakening, fault narrowing, and earthquake cyclicity.
A model based on incremental stress rheology and rock texture dynamics is introduced that emphasizes the interplay of rock competency, porosity, and other texture variables with stress and strain. The deformation mechanisms taken into consideration are poroelasticity and viscosity. The rheology equations are strongly coupled to the evolution equations of rock texture and pore fluid flow.
The model is used to gain an understanding of several oscillatory modes of fault movement. The roles of rock competency, fluid pressure, and continuous deformation in these oscillations is illustrated for various conditions. The approach is shown to be a natural starting point for a theory of the three-dimensional, multiprocess dynamics of fault nucleation, growth, morphology, reactivation, and continuous versus seismic behavior.