Development of fault discontinuities in shear experiments

Shear experiments using clay and fault gouge cakes were performed to study the origin of discontinuities along strike-slip faults. Simple, continuous strike-slip faults initially nucleated in the samples, and they were separated from each other. Discontinuities began to develop when these faults interacted each other. Two processes were especially important for the development of fault discontinuities: cross faulting which caused segmentation and offsetting of originally continuous faults, and fault interaction which changed fault propagation paths, created various types of bends, abandoned some old fault segments, and caused coplanar faults to avoid each other. Cross faulting created type I fault discontinuities in which all fault segments in a fault stepped in one direction (either all left or all right), and fault interaction created type II discontinuities in which fault segments in a fault stepped in both directions. The experimental results are compared with some natural fault patterns to demonstrate that this type of experiments can be used to investigate the origin of discontinuities along natural strike-slip faults. (C) 1998 Elsevier Science B.V. All rights reserved.