Accuracy of Picoseismic Catalogs in Hectometer-Scale In Situ Experiments

Understanding the seismicity and hydromechanical processes during hydraulic stimulation in hectometer-scale in situ experiments is crucial for bridging the gap between laboratory studies, decameter-scale in situ experiments, and large-scale geothermal projects. These insights can help to optimize the use of geothermal energy. A key example of this is the Bedretto Underground Laboratory in Switzerland, where multiple hydraulic stimulation experiments were conducted between 2021 and 2023 at a hectometer scale. In this study, we present modifications of standard seismic event processing techniques for mesoscale experiments, enabling the accurate detection and location of picoseismic events at these scales. We differentiate between the needs of seismic catalogs for rapid hazard assessment, which require real-time detection of large-magnitude events, and postprocessed catalogs, which are essential for detailed analysis of activated fracture networks, for which a complete seismic catalog is essential. In addition, we evaluate the impact of picking accuracy, background 1D velocity model, and network coverage on the final event locations within a mesoscale underground 3D seismic network, a novelty in experimental seismology.