Determining brittle extension and shear strain using fault length and displacement systematics: Part II: Data evaluation and test of the theory

We use the theoretical relations developed in Part I of this work to evaluate the self-consistency of fault-length and fault-displacement data gathered in domains of one and two dimensions from the Yucca Mountain area and from the coalfields in south Yorkshire, U.K. These data sets are not all self-consistent. For the Yucca Mt. area, the theory shows that, the volume over which the sampling of the faults must occur should have a horizontal width no smaller than 2.4 times the horizontal length of the largest fault, and a depth no smaller than 1.6 times the vertical extent of the largest vertical-equivalent-fault. It also shows that the volumetric extension must be ≥95% of the extension of a two-dimensional domain and ≥80% of the extension of a one-dimensional domain. The theory successfully accounts for the observed cumulative extensional strain derived from fault-displacement data from a one-dimensional sampling domain at Yucca Mt., Nevada, U.S.A. Faults up to about four orders of magnitude smaller than the largest fault make a significant contribution to the strain. The most robust calculation of cumulative fractional strain requires the parameters inferred from sampling displacement in a one-dimensional domain. This sampling procedure therefore provides the most reliable results.