Since 2012 many wind turbines have been installed on the Frankonian Jura and a number of them also in the vicinity of stations of the Gräfenberg array (GRF), consisting of 13 broadband stations within an area of about 50x100 km. It has been shown that these turbines take a significant effect on the noise level at many of the GRF station sites (Stammler & Ceranna, 2016, reference below). The array as a whole suffers from a deterioration of its sensitivity to teleseismic events of more than 0.1 magnitude units at wind speeds above 3.5 m/s (in 10m height). At individual station sites the noise signatures at frequencies above 2 Hz can be attributed to close-by wind turbines observing an approximate power decay law with increasing distance to the recording site. At a frequency of about 1.1 Hz, however, at most stations the strongest influence is visible, but the relation between measured PSD amplitudes and turbine distances does not support a simple decay law when taking into account only the closest wind turbine locations. This suggests that for this frequency turbines at larger distances play a role. This investigation tries to model the propagation of the turbine induced noise and to explain the observed PSD values at the GRF stations. As a result the contributing turbines can be identified as well as average propagation properties for the noise waves determined.
Influence of Wind Turbines on Seismic Records of the Gräfenberg Array, Klaus Stammler and Lars Ceranna, Seism.Res.Lett. (2016) 87(5): 1075-1081, https://doi.org/10.1785/0220160049