Kinematic analysis of fault-slip data

Abstract

An array of graphical and numerical techniques facilitate qualitative and quantitative kinematic analysis of fault-slip data. Graphical contouring and Bingham statistics of the shortening and extension axes for kinematically scale-invariant faults characterize the distributions and orientations of the principal axes of average incremental strain. Numerical analysis by means of moment tensor summation yields the orientations and magnitudes of the principal strain axes as well as rotational information. Field data can be weighted for moment tensor summation using measurements of fault gouge thickness and/or fault plane width, from which average displacement and fault area can be estimated. The greatest uncertainties of kinematic analysis derive from assumptions about the weighting of the data, the effects of post-faulting rotation on the data, the degree to which sampling is representative of the entire fault population, and the spatial homogeneity of strain. These assumptions can be evaluated for a specific data set. Geometric criteria can distinguish the kinematic heterogeneities produced by triaxial deformation, anisotropy reactivation, strain compatibility constraints and/or multiple deformations. Strain compatibility, material anisotropy and heterogeneity may be characterized by integrating the results of kinematic and dynamic fault-slip analyses.