Spatio-temporal characteristics of the ambient seismic noise field at the EMR gravitational wave telescope candidate site

Ambient seismic noise has the potential to significantly reduce the detection capabilities of the planned next generation gravitational wave detector (so-called Einstein telescope). The noise field impacts the detector performance either directly by transferring seismic movements into the detector system or indirectly by changes to the gravitational attraction of the surrounding rockmass due to spatio-temporal density changes caused by seismic waves (so-called Newtonian noise). In order to find the best geometries for the placement of the subsurface detection chambers, allow for active suppresion of detector vibrations and estimate the influence of Newtonian noise, a precise knowledge of the local ambient seismic noise field at the surface and at placement depth is vital. In this context, the amplitudes, source locations and durations of distinct natural and anthropogenic noise sources of the ambient noise field are all of interest.

Here, we present first results from investigations in the EMR region (Euregio Meuse-Rhine) Einstein telescope candidate site in area between Maastricht, Liège and Aachen. Data was recorded by several temporary deployments of short period sensors running for several weeks each. Possible noise sources in this region include ocean microseism from the North Sea/North Atlantic for frequencies below 1 Hz and wind farms, transportation infrastructure like highways and railways and heavy machinery as anthropogenic sources in the frequency range above 1 Hz. Apart from spectral analysis to determine the frequency resolved spatio-temporal amplitude changes at the recording sites, we also investigate the signal coherence over the network to estimate frequency bands, time intervals and (sub-)networks that could be used for further coherence based analysis. We then apply classical array analysis and Matched Field Processing (MFP) to pinpoint possible source locations of the seismic wavefield outside and within the posssible placement area of the Einstein telescope candidate site.