Key points:

• The dominant azimuth of the maximum horizontal stress magnitude (SHmax) is oriented NNW-SSE. This orientation is consistent in all the siting regions in the Mesozoic sediments and the pre-Mesozoic basement rocks.
• Characteristics of the stress field are similar in all three siting regions, with depth and mechanical layering coupled to tectonic loading controlling stress magnitudes.
• Tectonic loading has led to higher stress magnitudes in more competent calcareous layers and can explain why tectonic overprint in these layers is often more pronounced than in the weaker clay-mineral-rich layers.
• In the three siting regions the spatial characteristics of the present-day stress field can be predicted with geomechanical-numerical models with the same degree of reliability.
• The Opalinus Clay exhibits very consistent gradients of the stress magnitudes, irrespective of the siting region considered. Minor differences in the stress regime (i.e. ratios of horizontal to vertical stress) between regions arise mainly from the different depths of the Opalinus Clay.