Abstract
This study examines ambient seismic noise recorded from operational seismic monitoring stations installed on offshore wind platforms in the Yellow Sea. The research utilizes one-year three-component continuous waveform data to investigate energy intensity, wavefield composition, and polarization properties through frequency-domain polarization analysis. A dynamic finite element analysis is conducted on a typical offshore platform structure to investigate the amplification effect. The results show that: (1) The energy of single-frequency microseisms is clearly observable, while distinct segmentation phenomena are observed near 0.2 Hz within the double-frequency microseism (DF) band, with short-period DF exhibiting stronger energy than long-period DF. The wind, wave and current may result in greater horizontal noise energy intensity than vertical components at specific frequencies and directions; (2) The ambient seismic noise recorded at offshore platform monitoring stations exhibits systematic amplification compared to onshore station observations, with an average amplification factor of 3-5 across the studied frequency band. Notably, maximum amplification reaches 6.6-7.7 times within the 1.2-1.6 Hz range, representing a significant resonant response characteristic of the offshore platform structures. (3) Within the microseismic band (20 s-0.5 Hz), the azimuth of the noise polarization principal axis predominantly clusters around 200°. The polarization degree exhibits perturbed variations with frequency between 0.2-0.6 Hz and is slightly greater than that obtained from onshore stations. These observations indicate that hurricane/storm activities and short-period ocean waves in the relevant maritime area, along with their breaking and turbulent processes, generate pronounced high-frequency noise components.