Effects of propagation rate on displacement variations along faults

Abstract

Field observations indicate that much of the variability in the displacement—distance ( d−x) profiles and length—displacement relationships of faults is caused by factors which can affect the propagation of faults. These factors include the interaction and linkage of segments, fault bends, conjugate relationships and lithological variations. Existing models for the d−x profiles of faults do not take these effects into account. Fault development can be modelled assuming faults accumulate displacement by a series of slip events, and using a function ( p) to describe the rate of fault propagation. When p is constant during fault development, an approximately linear d−x profile eventually develops. When p decreases, such as when interaction occurs, the d−x profile rises above the linear profile. When p increases, the d3x̄ profile initially falls below the linear profile. Such variations in finite d−x profiles mean that the analysis of finite fault displacement gives little information about the d−x profiles of individual slip events. Variations in p cause variations in r/d MAX ratios (where r is the distance between the maximum displacement point and the fault tip, and d MAX is maximum displacement). Interaction tends to hinder propagation, but displacement continues to increase, causing relatively low r/d MAX ratios. Inelastic deformation can occur at fault tips, especially where strain is concentrated at oversteps, causing steep d−x profiles and low r/d MAX ratios to develop.