On two interacting creeping vertical surface-breaking strike-slip faults in a two-layer model of the lithosphere

Abstract

Two aseismically creeping long vertical surface-breaking parallel strike-slip faults are taken to be situated in an elastic layer, resting on and in welded contact with a visco-elastic halfspace, representing the lithosphere-asthenosphere system. Solutions are obtained for the displacements, stresses and strains, using a technique involving the use of Green's functions and integral transforms, for three possible cases-the case of the absence of any fault creep, the case in which one fault is creeping and the other is locked and the case in which both faults are creeping, taking into account the displacements and stresses present initially, and assuming that the tectonic forces maintain a shear strain far away from the faults. The types of fault creep for which the displacements, stresses and strains are finite everywhere in the model near the faults are identified, and the conditions satisfied by these types of fault creep are determined in a simple form. Fault creep across a fault is generally found to reduce the rate of accumulation of shear stress near the fault. The effect of aseismic creep across one fault on the shear stress near the other fault is found to depend on the distance, dimensions, relative position and other characteristics of the two faults. Fault creep across one fault is generally found to reduce the rate of shear stress accumulation near the neighbouring fault in the theoretical model considered. Under suitable circumstances, aseismic creep across one of the faults is found to result in aseismic release of shear stress near both faults, thus reducing progressively the possibility of a sudden fault movement generating an earthquake. The influence of one creeping fault on another is found to decrease rapidly with increase in the distance between the faults. The possible uses of the model in the study of the interaction between neighbouring strike-slip faults in a layered model representing the lithosphere-asthenosphere system and in the estimation of return times of earthquakes is examined. © 1992.