A mechanism of stress accumulation near a strike-slip fault

Abstract

A vertical strike slip fault, situated in VISCO-elastic layer, representing the lithosphere is considered. The upper part of the fault is assumed to remain locked, except during an earthquake, when it slips. It is assumed that the lower parts of the fault slip past each other. It is also assumed that tectonic forces maintain a shear stress far away from the fault. Exact solutions are obtained for the displacements and stresses in the system and it is shown that gradual accumulation of shear stress would occur in the neighborhood of the fault. There would be considerable amplification of shear stress on the locked part of the fault, leading finally to a sudden slip of the upper part of the fault under suitable circumstances. The mathematical results are compared with some relevant observations on the surface deformations in the neighborhood of strike-slip faults. It is shown that such comparison can be used to obtain estimates of the probable time of sudden fault slip, if sufficient data are available, and would also lead to estimates of the ratio of the effective viscosity of the lithosphere in the neighborhood of the fault and the shear stress maintained by tectonic forces far away from the fault. It is also shown that the results are likely to be useful in obtaining greater insight into the problem of earthquake prediction and in estimating the changes of seismic risk with time near an active fault.