Fault propagation and segmentation: insight from the microstructural examination of a small fault

Naturally formed faults typically are segmented. The detailed microstructural examination of a small brittle fault in the Shawangunk Mountains of Ulster County, New York provides new insight into the segmentation process. In brittle faulting the propagation directions of faults can be determined from the orientations of microfractures formed within the process zone. We have determined the propagation directions at several locations along this strike-slip fault and these directions indicate growth of individual segments from the segment centers toward the tips. This information, combined with observed fault geometry, allows us to reconstruct a plausible growth history of this segmented fault and of the formation of the segment boundaries.