EARTHQUAKE RECURRENCE-TIME VARIATIONS WITH AND WITHOUT FAULT-ZONE INTERACTIONS

The macroscopic behaviour of a fault zone can be described by a classi c Coulomb friction law and static-kinetic rheology. The critical failu re stress leading to the activation of a single shear zone segment the n depends on the normal stress acting on the future fault plane. It is known that the seismic cycle on a main fault patch can be modulated b y surrounding fault activations, leading to interaction with the main segment, or by other external stress perturbations. The results presen ted here stem from analytical assessments and 2-D numerical elastic mo dels. They show that an earthquake recurrence-time variation with cont inuing deformation system development is not necessarily connected to fault interaction processes under the above assumptions. Instead, aper iodicity can result from a non-ideal orientation of the rupture plane in the simplest possible homogeneous stress field, even when constant loading rate and frictional parameters are assumed. This effect can st ill be found in the multifault geometries we studied, where the intera ction of segments determines the seismicity patterns of the system to varying extents. Our results suggest that a stable earthquake periodic ity on non-changing fault sets will seldom be found in nature. We prop ose a reconsideration of the ideas leading to a hypothesized steady se ismic cycle in earthquake prediction models.