Frictional slip and fractures associated with faults and fold

Fractures are not uniformly distributed throughout the earth but often occur within clusters. These fracture clusters may serve as conduits for the flow of fluids through the earth's crust. Fracture localization has been observed in rock outcrops near faults, within folds and at the edges of pre-existing fractures. Laboratory and numerical experimental investigations provide insights on the conditions that promote and discourage development of fracture clusters.;Mixed mode I+III loading of a single fracture front results in out-of-plane propagation into multiple echelon stepping fractures. Within my laboratory experiments, the observed angle of twist of echelon fractures increases with the ratio $Ksb{rm III}/Ksb{rm I}$ and falls below theoretical predictions. I propose that interaction among growing fractures may contribute to this discrepancy.;Fracture clusters are often associated with folding; understanding folding mechanics will help us predict fracture localization which may control fluid flow. I postulate that the clustering of joints within folds may in part be due and slip along layer contacts (bedding-planes). Numerical experiments investigate the deformation of frictional bedding planes near dipping faults. I compare these mechanical modeling results to kinematic models of fault-propagation folds and conclude that mechanical models offer important insights to better understand the folding process. The fault models are also used to examine the influence of frictional bedding-plane slip on blind thrust fault propagation. Bedding-plane slip may have important implications for the assessment of seismic hazards. I analyze multilayer flexure by comparing field observations from East Kaibab Monocline, Utah with results of numerical experiments. The numerical models examine a flexed multilayer which simulates the Navajo Formation at Hackberry Canyon; the first-order results match field observations. These studies demonstrate that frictional bedding-plane slip contributes to folding and the development of flexural-slip associated joints.;Joints may also clusters along faults elucidating the mechanical processes of faulting and influences fluid flow. I use numerical models to examine conditions of joint localization with experimentally determined limits on rock surface friction. The friction distribution along faults controls slip distribution and influences fracture localization.