Geology, and particularly the composition of the rock layers, determines which site is most suitable for a deep geological repository.
To complete the overall picture of the underground geological environment in Northern Switzerland, Nagra has complemented existing knowledge with additional investigations. These include seismic measurements, Quaternary investigations, deep boreholes and high-precision altimetry. In addition, very weak earthquakes are recorded and analysed.
Ideally prepared for the siting proposal
Through its investigations, Nagra knows what the geological underground looks like in the regions that are suitable for a deep geological repository. It has identified where the most suitable rock formations are situated and what properties they possess. It also knows the locations of so-called fault zones that must be avoided when constructing a repository.
Nagra is now ready to compare the potential siting regions for a deep geological repository with each other. In 2022, it will announce which site it considers most suitable for a repository.
Measurement network for satellite altimetry
Nagra operates a measurement network for high-precision navigation satellite altimetry to detect minute movements of less than one millimetre per year in the geological underground of Northern Switzerland. The data on movements below ground are collected over several years and are used to refine geological models and predictions for the long-term safety of a future repository.
Measurement network for minor earthquakes
On behalf of Nagra, the Swiss Seismological Service operates a seismic monitoring network to detect minor earthquakes. This also includes monitoring Nagra’s deep boreholes. The measuring instruments (seismometers) are installed in remote areas to minimise the impact of the local population. This network makes it possible to record and determine the depth of earthquakes that are so weak that they cannot be detected by humans. An accurate understanding of seismic activity in a region is important for assessing the long-term safety of a deep geological repository. By analysing earthquakes, active fault zones can be identified and located.