The research groups “Simulation in Applied Mechanics” of Dr. Stefan Kollmannsberger at the Chair for Computation in Engineering and Computational Modeling and Simulation and the research group “Geothermal Energy” at the Chair for Engineering Geology by Prof. Kurosch Thuro, get to the bottom of questions about crack propagation and its precise simulation. In deep geothermal energy, the failure mechanism in the reservoir rock plays an extremely important role. In the past, in the course of geothermal extraction, microseismic events have occurred at geothermal projects, which were triggered by fracture processes and the displacement of subsurface interfaces. A precise underground model with a corresponding simulation can help to identify major risks in advance. However, reservoir and borehole stability modeling often works with simple literature values ​​or assumptions of the geomechanical rock and rock parameters. As a consequence, that fracture behavior and crack propagation in the rock can only be predicted imprecisely. The topics of reservoir and borehole stability should be therefore increasingly addressed within the framework of the Geothermal-Alliance Bavaria. The characterization of reservoir rocks should be supplemented by a digital model, which includes not only the facies but also the fracture behavior. Computer tomography methods, high-speed cameras and acoustic emission are used as the basis for building the digital model. As a little foretaste, the performance of the high-speed cameras is presented in this video contribution of the sub-project based at the Chair of Engineering Geology together with a short project description.