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Previously conducted underground investigations in the siting regions

The underground in Northern Switzerland has been thoroughly researched. Boreholes and seismic measurements have contributed significantly to obtaining an overall image.

Nagra and other companies have investigated the geological underground of Northern Switzerland using various methods. Points indicate borehole investigations whose data are included in the siting decision. Areas and lines indicate seismic surveys. The three potential siting regions for a deep geological repository are: Jura Ost (left), Nördlich Lägern (centre) and Zürich Nordost (right).

Geology, and particularly the composition of the rock layers, determines which site is most suitable for a deep geological repository.

Wissenschaftler begutachten eine Gesteinsprobe
Scientists inspect a rock sample retrieved from below ground.

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.

Seismik-Messungen der Nagra in der Nähe des Kernkraftwerks Gösgen
Seismic measurements conducted by Nagra in the vicinity of the Gösgen nuclear power plant. Photo: Beat Müller
Quartärbohrung der Nagra in Untersiggenthal
Nagra’s Quaternary borehole in Untersiggenthal.

Further information:

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.

Messstation für satellitengestützte Höhenmessungen in Seltisberg
Measuring station for satellite altimetry in Seltisberg, Canton Basel-Landschaft.

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.

Messtation des Schwachbebennetzes in Böbikon
Measuring station in Böbikon (Canton Aargau) as part of the minor earthquake detection network set up by the Swiss Seismological Service. Photo: Beat Müller

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