FBF is a series of modular programs coded in ANSI C++ to simulate thrust and normal faulting in cross section. The employed deformation function preserves area and therefore balanced cross-sections can be obtained with these programs. The programs run in text mode and the source code can be ported to and compiled on most computer platforms.

The package consists of a preprocessor, a processor, and a postprocessor. The preprocessor generates meshes that represent stratigraphic units in their undeformed state. Units in the initial state can have tabular geometries, thin laterally, or a composite geometry. The processor carries out a forward simulation to obtain the dislocated state of the units induced by a fault of known shape and displacement. Finally, the postprocessor converts the processor output to a format suitable for plotting.

The structural models obtained with the package are in good agreement with structures observed in fold-and-thrust belts and in extensional areas. Moreover, FBF can be used to test activity sequences of faults, to calculate potential fields associated with subsurface structures, and to simulate more complex geological systems and processes such as the stratigraphic response to synsedimentary brittle deformation.