3 Tectonic regimes, Fracture Patterns and Reactivation

This section discusses

• how the orientation of tectonic stresses near the Earth’s surface, and the
• respective tectonic regimes, control the fracture orientation patterns;
• how joints, hybrid fractures and faults can be recognized on rock exposures; and,
• the reason why reactivation of existing weakness planes is a very common mechanism, causing the lithological types to strongly influence the configuration of the fracture system in a rock mass. Planes susceptible to being reactivated include an existing anisotropic feature, such as foliation, and discontinuities, such as veins or fractures.