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 propagated underground 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 cross-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 small structural irregularities.
In contrast with 2D seismic methods, which reveal information only along the seismic lines, 3D imaging provides information continuously through the subsurface within the bounds of the 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 1st October 2015. Supplementary seismic measurements followed in the Zürich Nordost siting region at the beginning of 2016. 3D measurements are planned in the Nördlich Lägern siting region in winter 2016/17.
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 over an area of 50 square kilometres|
|2011/12||305 profile kilometres|
|2015/16||3D seismics covering an area of 110 square kilometres|
Regional seismic investigations in 2011/12. Vibrator vehicles are used to generate acoustic waves. Suspended from the cable in the foreground are geophones that record the signals generated by the sound waves. Image: B. Müller