The effect of non-parallel thrust fault interaction on fold patterns

Abstract

The geometry of two subsurface non-parallel thrust faults are systematically altered within mechanical models to determine the range of resulting fold map patterns and the effect of fault interaction on these fold patterns, and ultimately to infer fault geometry from complex fold shapes. Multiple faults can create both complex fold patterns with more than one fold axis and single folds without evidence of a second fault. Fold length may not correlate to fault length when remote contraction is oblique to the faults; thus contraction direction should be determined before fault length is inferred. The influence of fault interaction is studied by comparing the fold pattern created by interacting faults to the fold pattern created from the superposition of folds produced by equivalent but isolated faults. Under small strains, larger faults tend to have greater interaction but even interacting faults may not produce fold patterns notably distinct from the superposed fold patterns. This suggests that fault interaction need not necessarily be considered when inferring fault geometry from fold shape in the field; however, under non-coaxial strain conditions fold patterns may differ from those presented here.