Structural control on stress variability at Forsmark

The in situ stress state is a key rock mechanics parameter and it must be well understood for the design of an underground repository of spent nuclear fuel. The current stress state in the Fennoscandia area is dominated and driven by Mid-Atlantic ridge push and collision of the Eurasian and African plates in the Alps. Additionally, earlier glaciation cycles have changed stress conditions remarkably and promoted the shear of brittle fault zones thereby causing changes in the stress field. In the thrust fault conditions that have been dominant for a long time, shallow dipping faults have been, and are still, prone to slip.