Periodic loading on a creeping fault: Implications for tides

We study the effect of time varying normal and shear stress perturbations o n a creeping fault and in which inertia is neglected. When interpreted in t erms of earthquake triggering by earth tides, our results suggest that tida l triggering may exist but be very difficult to detect. We use a spring-blo ck model with a rate-and state dependent friction law, loaded at constant v elocity, and in which inertia is neglected. When a periodic stress is appli ed, a resonance exists which can destabilize sliding (i.e. earthquakes). Ho wever, when frictional parameters slightly vary along the fault, the observ ed phase lag between the response of the fault and the perturbating stresse s close to resonance shows a broad and uncorrelated scattering.