Thickness-Displacement Relationships for Fault Zones
Journal of Structural Geology
Fault zone thickness and displacement data have been used in recent studies to infer a global linear relationship between the two parameters in log-log space, and based on this empirical relationship, several models of fault growth have been proposed. Examination of the original data sets, but on linear graphs, indicates that there is a wide statistical variability of many of the data, and that larger values of displacement along faults are only generally related to an increase of fault zone thickness. The earlier data do not confirm a thickness-displacement relationship for faults of similar displacement, nor for faults in similar rock types. Reasons for the lack of correlation may be the wide range of rock types, structural settings, and processes responsible for the development of the faults measured. An example of thickness variations along the Bismark fault, southwest Montana, shows the variations of fault zone thickness along strike and down plunge. Conceptual and quantitative models which rely heavily on thickness-displacement relationships should be considered with caution until further data are collected on the topic. Future studies should explicitly state the criteria used to determine faulted and unfaulted rock, present in explicit form the slip vector used to determine net offset, and present, if possible, measurements of thickness and displacement from: (1) different points along the same fault, (2) families of faults in similar rock types with different amounts of slip, and (3) faults with similar amounts of net slip in similar structural settings.
Evans, J. P., 1990, Thickness-displacement relationships for fault zones, J. of Structural Geol., v. 12, p. 1061-1066.