As part of the European research project Seismic Imaging Techniques for Mineral Exploration (SIT4ME), in-mine seismic active-source and continuous noise measurements were performed within an underground mine gallery of a former radioactive waste repository – the Asse II salt mine (Lower Saxony, Germany) to investigate its geological conditions. Inspired by recent underground active-seismic surveys in the Cote Blanche salt mine and former In-seam seismic surveys in the German hard-coal district of the Ruhr area, we apply conventional exploration and processing methods to an image of the subsurface. Among others, these include data sorting, bandpass filtering, normal moveout correction, static correction and depth (distance) conversion. To process the passive seismic data, we perform an illumination diagnosis for the retrieval of body-wave arrivals and apply passive-source seismic interferometry by cross-correlation (PSICC) on noise data dominated by S-waves. We show that active-source seismic measurements can be used from underground mine galleries for the identification of geological structures. Furthermore, we demonstrate that PSICC can be used to produce virtual-source underground seismic surveys resembling an active-source seismic survey.@en

To test passive seismic interferometry (PSI) in underground mining environments, we carried out an active-source seismic and continuous noise measurement in a mine gallery of a former radioactive waste repository - the Asse II salt mine (Lower Saxony, Germany). To analyze the active-source data, we process the data inspired by conventional seismic processing techniques. On the contrary, for the passive-source data, we first perform an illumination diagnosis to identify and separate seismic wave types. Subsequently, we apply PSI by cross-correlation for the retrieval of body-wave arrivals and finally apply selective-stacking. In this context, we refine processing procedures for PSI inside of mine galleries and point out that data recordings of <24 h and summation times of 10 min to 30 min during selective stacking are sufficient when applying PSI to underground noise data. Using PSI imaging results, we identify several pre-known and unknown geological structures exceeding the number and distance of structures determined from active-source imaging results. Here, PSI showed advantages over the active-source seismic data regarding resolution, energy distribution, and spatial extent.

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