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Physical Modeling to Establish Controls on Fracture Development in Basement-Involved Fault-Related Folds

D. P. Keating
Northern Illinois University, Department of Geology and Environmental Geosciences, DeKalb, IL

The architecture of fracture systems that form in fault-related folds is controlled by a variety of stratigraphic, structural, and environmental factors. This study uses physical modeling, field and seismic data, and computer modeling to establish and test relationships between structural factors and fracture system architecture in basement-involved fault-related folds; it specifically investigates how fracture system architecture may be controlled by the geometric and kinematic evolution of the fault-fold system. Because the fold geometry is always changing as the fault-fold system evolves, different regions of the fold will experience varying degrees and orientations of stress and strain throughout the evolution of the structure.

I employ a novel electronically-controlled physical-modeling machine developed at Northern Illinois University for the first part of the study. Models will consist of a layer of clay overlying a rigid basement of thin plastic strips, each of which can move independently. The design of this machine will allow me to vary the 3-D geometry of the basement fault, the shape of the fault displacement profile and the net convergence direction with respect to fault strike. Model basement faults can grow laterally as they accumulate displacement and the manner in which displacement accrues can be controlled by the user. The total modeling area is nearly 1 square meter, facilitating the use of long faults and relatively large displacements. Although models will not be precisely scaled to duplicate geologic deformation, preliminary results produced qualitative geometric and fracture data that are strikingly similar to natural basement-involved fault-related folds.

AAPG Search and Discovery Article #90902©2001 AAPG Foundation Grants-in-Aid