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

Abstract

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.

Simulation of ground motion emissions from wind turbines in low mountain ranges: implications for amplitude decay prediction

“…A value of b amp = 0.5 (b PSD = 1) is the theoretical value for geometrical spreading of surface waves in the far-field in elastic, laterally homogeneous media. Nevertheless, b PSD -values<1 are found in several studies [Zieger and Ritter, 2018, Neuffer et al, 2019, Limberger et al, 2021, Neuffer et al, 2021 especially for low frequencies (<5 Hz). The reason for this may be the interference of the wavefields of several WTs.…”

“…The influence of multiple sources [Limberger et al, 2021] and topography [Limberger et al, 2022] have already been analyzed in previous studies, but still few simulation case studies for WT emissions are available, despite the need to better understand this phenomenon to protect sensitive infrastructure. In our work we use a finite difference (FD) approach to simulate ground motions and focus on directional dependencies, attenuation (Q) and source characteristics.…”

Joint Analysis of Resident Complaints, Meteorological, Acoustic, and Ground Motion Data to Establish a Robust Annoyance Evaluation of Wind Turbine Emissions

“…[33,35]). Modelling of WT related ground motion propagation can be studied analytically for homogeneous subsurfaces [42] or by the application of finite-element modelling for arbitrary subsurface (e.g., Ref. [43]), but is beyond the scope of this paper.…”

The earth-fill dam state express investigation using mechanical vibrations produced by HPP

“…It was shown that in microseism spectra there are thin peaks corresponding to monochromatic signals. Such peaks were ubiquitous [24][25][26][27][28][29][30], even at the ocean bottom [31]. Researchers were revealed their main properties such as small variations in main frequencies and their harmonics over time, correlated with variations in the frequency of the electrical network.…”