Preprints
https://doi.org/10.5194/se-2021-21
https://doi.org/10.5194/se-2021-21

  11 Mar 2021

11 Mar 2021

Review status: a revised version of this preprint is currently under review for the journal SE.

Seismic radiation from wind turbines: observations and analytical modeling of frequency-dependent amplitude decays

Fabian Limberger1,2, Michael Lindenfeld1, Hagen Deckert2, and Georg Rümpker1 Fabian Limberger et al.
  • 1Institute of Geosciences, Goethe-University Frankfurt, 60438 Frankfurt am Main, Germany
  • 2Institute for Geothermal Resource Management (igem), 55411 Bingen, Germany

Abstract. In this study, we determine spectral characteristics and amplitude decays of wind turbine induced seismic signals in the far field of a wind farm (WF) close to Uettingen/Germany. Average power spectral densities (PSD) are calculated from 10 min time segments extracted from (up to) 6-months of continuous recordings at 19 seismic stations, positioned along an 8 km profile starting from the WF. We identify 7 distinct PSD peaks in the frequency range between 1 Hz and 8 Hz that can be observed to at least 4 km distance; lower-frequency peaks are detectable up to the end of the profile. At distances between 300 m and 4 km the PSD amplitude decay can be described by a power law with exponent b. The measured b-values exhibit a linear frequency dependence and range from b = 0.39 at 1.14 Hz to b = 3.93 at 7.6 Hz. In a second step, the seismic radiation and amplitude decays are modeled using an analytical approach which approximates the surface-wave field. Since we observe temporally varying phase differences between seismograms recorded directly at the base of the individual wind turbines (WTs), source-signal phase information is included in the modeling approach. We show that phase differences between source signals have significant effects on the seismic radiation pattern and amplitude decays. Therefore, we develop a phase-shift-elimination-method to handle the challenge of choosing representative source characteristics as an input for the modeling. To optimize the fitting of modeled and observed amplitude decay curves, we perform a grid search to constrain the two model parameters, i.e., the seismic shear wave velocity and quality factor. The comparison of modeled and observed amplitude decays for the 7 prominent frequencies shows very good agreement and allows to constrain shear velocities and quality factors for a two-layer model of the subsurface. The approach is generalized to predict amplitude decays and radiation pattern for WFs of arbitrary geometry.

Fabian Limberger et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on se-2021-21', Anonymous Referee #1, 18 Mar 2021
    • AC1: 'Reply on RC1', Fabian Limberger, 20 May 2021
  • RC2: 'Comment on se-2021-21', Joachim Ritter, 12 Apr 2021
    • AC2: 'Reply on RC2', Fabian Limberger, 20 May 2021

Fabian Limberger et al.

Fabian Limberger et al.

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Short summary
Frequency-dependent amplitude decays of seismic signals induced by wind turbines are determined from (up to) 6 months of continuous recordings measured along an 8 km profile located at a wind farm in Bavaria/Germany. The radiation pattern and the amplitude decay of the induced signals are accounted for by an analytical approach that includes path as well as source effects. This approach is generalized to predict the characteristic seismic radiation patterns of arbitrary wind-farm configurations.