Datenpaket: Measures for seismic signal levels of wind turbine emissions

Seismic signals as are emitted by wind turbines can be rather narrow band and appear as distinct peaks in a spectral analysis. Nevertheless, their signal phase is suffiently stochastic so that power spectral density (PSD) is an accurate and robust measure of the signal level and its spectral distribution. A conservative smoothing over a narrow bandwidth (as small as 0.01 Hz) reduces the stochastic scatter while preserving the information on spectral variability.
Values of rms-amplitude in a finite bandwidth can easily be computed from PSD and would represent the time domain signal background. This measure is helpful to estimate the signal-to-noise ratio for earthquake peak amplitudes. Amplitude values, however, are somewhat arbitrary because they are larger the wider the chosen bandwidth.
A Jupyter notebook written in python is provided to test these concepts with various parameters on actual seismic recordings. A phase-coherent harmonic, for which PSD is mathematically infinite, is injected in the recorded data. By comparison with their signature the analysis demonstrates that the wind-turbine generated signals are not subject to scaling artefacts of PSD.

The results are summarized in a presentation given at the 2025 annual conference of AG Seismologie in Kiel (Germany) at the meeting of the task group 'Auswertung seismologischer Signale von Windenergie-Anlagen' (Evaluation of seismological signals from wind turbines).