The site selection procedure for high-level waste in Germany, as defined by the Standortauswahlgesetz (StandAG), involves the comparison of crystalline rock, rock salt and clay stone as potential host rocks for a Deep Geological Repository.

A potential repository site must be explored comprehensively and at high resolution, in order to provide essential data for its characterization and for the long-term safety assessment. High-resolution borehole seismic methods provide the detailed distribution of elastic parameters, however restricted to the close environment of the borehole. For a detailed and comprehensive site characterization, high-resolution methods are needed covering the full scale of an Underground Rock Laboratory (URL). In crystalline and rock salt environments, the ISIS system, developed by GFZ, has proven successful (link to ISIS project, section 4.2), but clay stone poses particular challenges to seismic exploration due to its heterogeneity, anisotropy and attenuation.

Since the Helmholtz Association joined the Mont Terri Project, the GFZ is provided with the access to the Mont Terri Rock Laboratory (Switzerland, Opalinus Clay) offering comprehensive opportunities for investigations on the characterization of clay formations around the rock laboratory. Within this project, seismic pilot surveys as well as repeat measurements will be acquired in order to investigate the potential of different seismic sources for high-resolution site characterization and to investigate the repeatability of such measurements for monitoring during the operational phase of a repository. The experimental work will be complemented by geophysical modelling on the resolution of seismic measurements in the rock laboratory scale.

Time frame

• 2018 - 2021

Funding

• BMBF - Federal Ministry of Education and Research
• Helmholtz Association

Principal Investigators

• Dr. Stefan Lüth (GFZ Potsdam)
• Dr. Rüdiger Giese (GFZ Potsdam)
• Prof. Dr. Charlotte M. Krawczyk (GFZ Potsdam)

Personnel

• Roman Esefelder (GFZ Potsdam)
• Britta Wawerzinek (GFZ Potsdam)

Cooperations

• Forschungszentrum Jülich (FZJ)
• Karlsruhe Institute of Technology (KIT)
• Helmholtz Centre for Environmental Research (UFZ)
• Helmholtz Zentrum Dresden Rossendorf (HZDR)

Methods & Equipment

• Methods: Seismic Exploration - Tomography and seismic reflection investigations
• Equipment: High-resolution seismic sources (GFZ underground seismic, ELVIS vibration source) seismic receiver systems (GFZ underground seismic, land streamer)

Publications/Results

• Wawerzinek, B., Lueth, S., Esefelder, R., Giese, R., Krawczyk, C. (2022 online): Performance of high-resolution impact and vibration sources for underground seismic exploration of clay formations at the scale of a rock laboratory. - Geophysical Journal International, ggac283.
  https://doi.org/10.1093/gji/ggac283
• Wawerzinek, B., Esefelder, R., Giese, R., Jurczyk, A., Krawczyk, C., Krüger, K., Lueth, S. (2022): Seismic pilot survey in the Mont Terri Underground Rock Laboratory (URL).
  https://doi.org/10.5880/GIPP.201999.1
• Esefelder, R., Wawerzinek, B., Lueth, S., Giese, R., Krawczyk, C. (2021): Seismic anisotropy of Opalinus Clay: tomographic investigations using the infrastructure of an underground rock laboratory (URL). - Swiss Journal of Geosciences, 114, 21.
  https://doi.org/10.1186/s00015-021-00398-2
• Lueth, S., Esefelder, R., Richter, H., Jaksch, K., Schwarz, B., Wawerzinek, B., Giese, R., Krawczyk, C. (2021): Licht ins Dunkel bringen. - System Erde, 11, 2, 18-23.
  https://doi.org/10.48440/GFZ.syserde.11.02.3