Seismic survey of the LUNA construction site

Picture of two seismometers used during the measurement. The instruments were placed on flagstones to improve coupling to the ground and buried to about 10 cm depth. The green seismometer is the one that will be installed in LUNA once the building is ready.) © ESA/DLR

As a lunar simulation facility, LUNA will also provide test and validation support for seismic experiments. A highly sensitive seismometer will be installed in the hall to continuously measure the seismic activity at the site and to feed the data obtained into the European Seismological Data Network.

In order to characterise the influence of the regolith and the hall on the seismic data, seismic measurements will be carried out at defined phases of the hall construction – for the first time in August 2023, after the asphalt surface has been removed from the former parking area and future moon simulation area.

Colleagues from DLR’s Microgravity User Support Center (MUSC), who have already put their geophysical skills to extraterrestrial use on a number of previous occasions, spent several days monitoring the construction site and were able to record both the signatures of global earthquakes and the movements of cars on the DLR site, as well as take-offs and landings at the nearby Cologne/Bonn airport.

During the measurements, construction work stopped in order to be able to measure the most realistic average spectrum for the area. Analysis of the measured data indicates that the subsurface at the LUNA site consists of a top layer of 16-18 m of sand on top of clay. The total sediment package on top of the bedrock at LUNA is approximately 190m thick.

The next measurement is planned for the fully constructed hall prior to regolith filling. 

Seismic registration of a car travelling along the road north of the LUNA construction site (bottom). The signals are generated by the car passing over man holes or other bumps in the road. The origin of the signals can be determined by using the time differences between their arrivals at the four spatially distributed seismometers (dark blue colour and white contour lines). The analysis shows that the car was travelling from east to west in this case (top). © ESA/DLR