Seismic surveys – looking into the geological subsurface
Seismic measurements provide images of the underground geological environment – a method comparable to ultrasound imaging. Seismic images capture information on the structure of the rock layers and the presence of geological fault zones.
Nagra and other companies have investigated the geological subsurface of Northern Switzerland and Wellenberg using various methods, including seismic measurements.
What are seismic measurements?
They are a type of ultrasound of the subsurface. Seismic measurements rely on vibrations that are generated artificially, i.e. by vibrator vehicles or by small charges exploded in boreholes at a depth of a few metres. The waves propagated underground are reflected by the different rock layers. Special sensors (geophones) at the earth’s surface register the reflected seismic signals.
What is the purpose of the recordings?
Scientists analyse the data, present the geological layers in the form of maps and prepare profile cross-sections.
The measurements provide information on the location and structure of the underground rock layers, particularly on their thickness, and the presence of fault zones. Modern seismic methods also provide information on certain rock properties and can reveal small structural irregularities.
Where were measurements conducted?
The interactive map provides an overview of the various seismic measurements conducted by Nagra in Northern Switzerland between 1982 and 1987. In 2011 and 2012, 2D seismic measurements were carried out in the Cantons Schaffhausen, Zürich, Aargau and Solothurn within the framework of Stage 2 of the site selection process for a deep geological repository.
From October 2015 to the beginning of 2017, 3D seismic investigations were carried out in the Jura Ost, Zürich Nordost and Nördlich Lägern siting regions. Additional 2D seismic measurements provided further information on the uppermost rock formations just below the surface. In contrast with 2D seismic methods, which reveal information only along the seismic lines, 3D imaging provides information over the entire survey area.