Impact of wind on ambient noise recorded by seismic array in northern Poland

Lepore, S., K.M. Markowicz, M. Grad

Geophysical Journal International

205(3), 2016, 1406-1413., 10.1093/gji/ggw093

Seismic interferometry and beam-forming techniques were applied to the ambient noise recorded during January 2014 at the ‘13 BB star’ array composed of thirteen seismic stations located in northern Poland. The circular and symmetric geometry of the array allowed the evaluation of the azimuths of noise sources and the velocities of recovered surface waves with a good reliability. After having pre-processed the raw records of the ambient noise in time- and frequency-domain, we studied the associated power spectral density to identify the frequency bands suitable for the recovery of the surface waves. Then the cross-correlation was performed between all the station pairs of the array to retrieve the Green's function, from which the velocity range of the surface waves can be determined. Making use of that analysis, the direction of the noise wavefield was linked to the maximum amplitude of the beam-power, estimated by the mixing in the frequency-domain of all the corresponding noise records. The results were related day by day to the mean wind velocity around Europe at 10 m above ground level obtained from global surveys carried out during the same month. Significant correlation between the direction of maximum beam-power associated to the ambient noise recorded at ‘13 BB star’ and the average wind velocity was found.