Interaction of parallel strike-slip faults and a characteristic distance in the spatial distribution of active faults

Abstract

SUMMARY A numerical simulation of the activities of many parallel strike-slip faults is performed to explore the effect of the interaction of fault slip on the spatial distribution of active faults. In the model, a large number of faults with random strengths are embedded in an elastic layer (lithosphere) over a Maxwell-type viscoelastic half-space (asthenosphere) and shear loading of a constant strain rate is applied. When slip takes place on a model fault, shear stress is decreased around the fault and then recovered with time due to the viscoelastic response of the asthenosphere. The decrease in shear stress prohibits the occurrence of another earthquake around the slipped fault, resulting in the existence of a characteristic distance between active faults. This characteristic distance is found to be controlled by the thickness of the elastic layer, the strain rate and the viscoelastic relaxation time. The density of simulated active faults increases with the strain rate, consistent with observations of active faults in Japan. Furthermore, the present simulation result may explain the characteristic distance which breaks the fractal structure of the spatial distribution of active faults in Japan, which was discovered by Lei & Kusunose (1999).