The rotation of the principal stress axes in a fault structure because of a rock stiffness contrast has been investigated for the impact of the ratio of principal stresses, the angle between principal stress axes and fault strike, and the ratio of the rock stiffness contrast. A generic 2D geomechanical model is employed for the systematic investigation of the parameter space.

It is generally assumed that faults have an influence on the stress state of the Earth’s crust. It is questionable whether this influence is still present far away from a fault. Simple numerical models were used to investigate the extent of the influence of faults on the stress state. Several models with different fault representations were investigated. The stress fluctuations further away from the fault (> 1 km) are very small.

When stresses yield a critical value, rock breaks and generate pathways for fluid migration. Thus, the contemporary undisturbed stress state is a key parameter for assessing the stability of deep geological repositories. In this workshop you can ask everything you always wanted to know about stress (but were afraid to ask), and this is divided into three parts. 1) How do we formally describe the stress field? 2) How do we to actually measure stress? 3) How do we go from points to 3D description?

Numerical methods can be used to estimate the stress state in the Earth’s upper crust. Measured stress data are needed for model calibration. High-quality stress data are available for the calibration of models for possible radioactive waste repositories in Switzerland. A best-fit model predicts the stress state for each point within the model volume. In this study, variable rock properties are used to predict the potential stress variations due to inhomogeneous rock properties.

Stress data predicted by a geomechanical–numerical model are mapped onto 3D fault geometries. Then the slip tendency of these faults is calculated as a measure of their reactivation potential. Characteristics of the faults and the state of stress are identified that lead to a high fault reactivation potential. An overall high reactivation potential is observed in the Upper Rhine Graben area, whereas the reactivation potential is quite low in the Molasse Basin.