| This study involved computer simulation of folding in order to predict the location of fractures which develop in a single layer fold and also to predict the region of greatest fracture density. The occurrence of fractures was investigated as a function of three variables: (1) the absolute viscosity of the competent layer, (2) the boundary velocities, and (3) the shear strength of the rock. The viscosity ratio, a dimensionless factor, controlled the fracture location and fracture density for the models tested. For high viscosity ratios (i.e., 1000:1) fractures developed in the outer region of the hinge of the fold early in folding history; however, for low viscosity ratio (i.e., 25:1) fractures developed in the inner region of the hinge first and the outer region of the hinge did not fracture until late in folding. The 10:1 viscosity ratio model only developed fractures in the inner region of the hinge. The boundary velocity (and average strain rate for the model), the absolute value of viscosity, and the shear strength affected the extent of fracturing, but the association between the stage in folding and the development of fractures in a particular location of the fold was independent of these three variables. (Abstract shortened by UMI.)... |
