The SpannEnD project – Towards a robust prediction of the 3D stress state in the upper crust of Germany

The assessment of the long-term stability of geological units in the context of subsurface use is a complex topic in which various geoscientific and technical aspects play an important role. For example, the geomechanical stability of radioactive waste repositories due to endogenous, exogenous and engineering processes is an important aspect in the long term. For a stability prognosis, an estimation of the recent stress state as well as an assessment of realistic future stress changes is required. However, data on the current stress state in the upper crust are incomplete, sparse and spatially unevenly distributed. Therefore, geomechanical-numerical models are the only possibility to estimate the complete stress tensor at locations where stress observations are not available. The SpannEnD project, had the goal to estimate the 3-D stress state in Germany. Therefore, a simplified subsurface model was created. Since stress data are essential for the calibration procedure, the first open access database for stress orientations as well as stress magnitudes was developed, which mainly summarises data from the study region. The best-fit stress model is assigned to the model which reproduces the results of many of the available magnitudes of horizontal stresses well. In the model region, there are numerous large-scale faults or fault systems that have an influence on the local stress state. However, the large number of faults could not be implemented as structural features in the geomechanical model. However, the modelled stresses are applied on the fault geometries to assess the fault reactivation potential.