University of Minnesota
Aerospace Engineering and Mechanics
Spring 1998 Seminar Series



Professor Michele Cooke
Department of Geology and Geophysics
Department of Civil and
Environmental Engineering

University of Wisconsin at Madison



Abstract


The flow of fluids through and across fault zones may be influenced by the distribution and orientation of associated opening-mode fractures. The development of fractures which form in response to fault slip can be investigated using linear elastic fracture mechanics (LEFM). The shape, orientation and density of secondary fractures depends on the location along the fault periphery. For example mode II deformation occurs where fault-tip line is perpendicular to slip direction along the fault, whereas mode III deformation dominates where the fault-tip line parallels the slip vector. The orientation of secondary fractures will influence the permeability anisotropy within rock around fault zones and has been investigated with standard LEFM and cohesive-end zone fault model. Within the field, we often observe multiple secondary fractures away from the tips of faults which cannot be explained within standard LEFM. One potential mechanism which could produce multiple secondary cracks is heterogeneous stresses along fault; slip gradients along faults produce stress concentrations which promote the development of opening-mode splay fractures. Since the slip distribution depends on the distribution of frictional strength along faults, spatial variations in the frictional properties may influence fracture localization. Variations in friction coefficient along faults can reduce the stress singularities at fault tips and promote the development of multiple fractures inwards from the fault tips.

Friday, June 5, 1998
209 Akerman Hall
2:30-3:30 p.m.


Refreshments served after the seminar in 227 Akerman Hall.
Disability accomodations provided upon request.
Contact Audrey Stark-Evers, Senior Secretary, 625-8000.