Glossar

 

Seismic surveys

Seismic measurements provide images of the underground geological environment using artificially generated vibrations.

The vibrations are generated by vibrator vehicles or small explosive charges (in boreholes a few metres deep). The waves propagate underground and are reflected by the different rock layers. Special sensors (geophones) at the earth’s surface register the reflected seismic signals.

Scientists analyse the data, present the geological layers in the form of maps and prepare profile sections. These provide information on the location and structure of the rock layers underground, particularly on thickness and the presence of fault zones. Modern seismic methods also provide information on certain rock properties and can visualise even small structural irregularities.

In contrast with 2D seismic methods, which reveal information only along the individual measuring lines, 3D imaging provides information across a whole survey area. Simultaneous scanning of the rock layers to great depths provides a three-dimensional image of the underground environment.

3D seismic measurements were carried out in the Jura Ost siting region from October 2015. Supplementary seismic measurements followed in the Zürich Nordost siting region at the beginning of 2016. 3D measurements were carried out in the Nördlich Lägern siting region in winter 2016/17.

More information on the exploration of the undergound (e.g. with seismic measurements or deep boreholes) can be found in Nagra's blog.

Nagra has carried out several seismic campaigns in the past:

1982 177 profile kilometres 
1983/84  220 profile kilometres
1991/92 235 profile kilometres
1996/97 3D seismics covering an area of 50 square kilometres 
2011/12 305 profile kilometres
2015/16 3D seismics covering an area of 110 square kilometres
2016/17 3D seismics covering an area of 90 square kilometres

 

Regional seismic investigations in 2011/12. Vibrator vehicles are used to generate synthetic sound waves. Suspended from the cable in the foreground are geophones that record the signals generated by the sound waves. Image: B. Müller

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