Displacements, segment linkage and relay ramps in normal fault zones

Abstract

A fault zone is produced by the displacement and linkage of component segments, and hence these are important to the understanding of fault zone-development. A small well-exposed normal fault zone at Kilve, Somerset, U.K., is described, which consists of 34 individual offset and linked fault segments. Antithetic faults appear to be associated with bending at relay ramps and foot wall uplift. A simple model is presented which assumes different displacement gradients inside and outside the influence of relay structures. High displacement gradients at the tips of offset fault segments produce lower r/dMAX ratios than those of isolated faults (where r = distance between the fault tip and point of maximum displacement, and dMAX = maximum displacement). Relay structures form between offset normal fault segments, producing inclined zones (relay ramps) whose geometry can be related to the displacement gradients at the fault tips. Linkage points between segments are marked by fault displacement minima, causing further complexity in displacement—distance data.