Assessing the seismic wavefield of a wind turbine using polarization analysis

Westwood, Rachel F.; Styles, Peter

doi:10.1002/we.2124

Cited by 13 publications

(6 citation statements)

References 19 publications

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“…Styles et al (2005) reported about discrete frequency peaks in seismic noise spectra that increase with wind speed and the rotation rate of a nearby WT and assigned the observed peaks to vibration modes of the WT tower and rotor rotation. Zieger and Ritter (2018) and Stammler and Ceranna (2016) confirmed discrete frequency peaks between 1 and 10 Hz and analyzed signal amplitude decays with distance to the WTs described by a power law. Saccorotti et al (2011) observed seismic signals with a frequency of about 1.7 Hz that were associated with WTs at distances of up to 11 km.…”

Section: Introductionmentioning

confidence: 72%

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

et al. 2021

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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 (PSDs) 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 seven distinct PSD peaks in the frequency range between 1 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 that 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 seven prominent frequencies shows very good agreement and allows the constraint of shear velocities and quality factors for a two-layer model of the subsurface. The approach is generalized to predict amplitude decays and radiation patterns for WFs of arbitrary geometry.

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Section: Introductionmentioning

confidence: 72%

“…The b factors derived by the various authors cover a broad range of values, even for similar frequency ranges. FloresEstrella et al (2017) published b values from 0.73 to 1.87 for frequencies between 2.7 and 4.5 Hz Zieger and Ritter (2018). derived values from 0.78 to 0.85 at 1-4 Hz and b = 1.59 at 5.5 Hz.…”

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confidence: 99%

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

et al. 2021

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“…Previous research suggests that mainly vertically polarized Rayleigh waves are emitted from WTs and dominate the WTinduced seismic noise (Westwood and Styles, 2017;Neuffer and Kremers, 2017;Gortsas et al, 2017). In our models, we assume surface-wave amplitudes to decay proportionally to r --1/2 (with distance to the source) due to geometrical spreading of the surface wave front on a cylindrical area in the 2D surface plane…”

Section: Surface Wavefield Approximationmentioning

confidence: 99%

“…Polarization analyses was used by Westwood and Styles (2017) to show that Rayleigh waves dominate the wave field emitted from WTs. This observation was confirmed by numerical simulations (Gortsas et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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

Limberger¹,

Lindenfeld²,

Deckert³

et al. 2021

Preprint

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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.

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“…The seismic energy generated by wind turbines (WTs) has been shown to propagate up to distances of 15 km and more (Schofield, 2001). This seismic energy or seismic noise can be measured by nearby seismic stations built for the detection of seismic events and/or seismic monitoring activities (Legerton et al, 1996;Rushforth et al, 1999;Schofield, 2001;Rushforth et al, 2003;Styles et al, 2005;Westwood et al, 2011Westwood et al, , 2015Stammler and Ceranna, 2016;Neuffer and Kremers, 2017;Westwood and Styles, 2017;Neuffer et al, 2019Neuffer et al, , 2021. The noise may result in the deterioration of the recording quality at seismic stations, therefore leading to a conflict between seismological station owners and WT operators (Neuffer et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Reduction of wind-turbine-generated seismic noise with structural measures

Abreu¹,

Peter

Thomas³

2022

Wind Energ. Sci.

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Abstract. Reducing wind turbine noise recorded at seismological stations promises to lower the conflict between renewable energy producers and seismologists. Seismic noise generated by the movement of wind turbines has been shown to travel large distances, affecting seismological stations used for seismic monitoring and/or the detection of seismic events. In this study, we use advanced 3D numerical techniques to study the possibility of using structural changes in the ground on the wave path between the wind turbine and the seismic station in order to reduce or mitigate the noise generated by the wind turbine. Testing a range of structural changes around the foundation of the wind turbine, such as open and filled cavities, we show that we are able to considerably reduce the seismic noise recorded by placing empty circular trenches approx. 10 m away from the wind turbines. We show the expected effects of filling the trenches with water. In addition, we study how relatively simple topographic elevations influence the propagation of the seismic energy generated by wind turbines and find that topography does help to reduce wind-turbine-induced seismic noise.

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Assessing the seismic wavefield of a wind turbine using polarization analysis

Cited by 13 publications

References 19 publications

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

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

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

Reduction of wind-turbine-generated seismic noise with structural measures

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