Vertical offset across the faults in the study area is less than the stratigraphic thickness of the Hickory, except along the southern parts of the faults bounding the graben. Consequently, along all faults, with the exception of the two noted fault segments, Hickory Sandstone is juxtaposed against Hickory Sandstone along a portion of a vertical section through the fault. Structure of Faults Lack of extensive outcrops allows only a generalized characterization of the structure of faults that juxtapose Hickory Sandstone against Hickory Sandstone. Outcrops of faults only show fault structure associated with sandstone intervals. There are no exposures of shear zones involving clay-rich interbeds.
Shear deformation associated with mappable faults is localized primarily in a well-defined zone.
Within this shear zone , shearing-induced comminution of the sandstone typically is not uniform but is localized along a number of closely spaced small faults. The occurrence of a conjugate system of small faults in a horizontal section reflects the existence of a strike-slip component of fault displacement. The average width of the shear zone of a fault appears to increase with increasing fault displacement, but this relationship could not be quantified. Enhanced development of small faults is observed adjacent to the shear zone of a large fault as compared to a location more distant from the fault. The orientation and density of small faults in this zone reflects the local strain field, which can differ from areas further from the fault.