Algorithm for Section Balancing Using Strain Compatibility Criteria

Declan G. De Paor, Dwight C. Bradley

Previous methods for balancing thrust-belt sections have relied on conservation of bed length and cross-sectional area, and admissibility of kink-fold geometry. Unfortunately, sections that incorporate these constraints may still represent physical impossibilities because they fail to meet strain compatibility criteria. Because rocks undergo discrete movements on fault surfaces and continuous deformation within fault slices, strain data should be incorporated in balanced sections. Finite strain markers are rarely available at critical points in a section, but the inferred geometry of fault ramps, fault flats, and bedding cutoff angles are implicit strain markers. Our algorithm integrates existing techniques of line and area balancing with compatibility criteria, allowing he user to unstrain and match hanging-wall and footwall fault geometries in the retrodeformed section. The program allows for area changes due to three-dimensional movement of material, and for individual beds to be treated according to competence.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.