Seabed Properties Derived from Ambient Noise

An extensive study of low-frequency ambient noise wavefields in the seabed has resulted in a new approach to determine the near-surface shear velocity. 33 minutes of continuous ambient noise recorded by an ocean-bottom cable (OBC) system without using an active source were analyzed for seafloor compliance and Scholte waves. Seafloor compliance was not observed and requires longer recording time. Scholte waves were observed in the frequency-wavenumber spectrum. The Scholte wave phase-velocity was modeled with a realistic one-dimensional near-surface model. The horizontal over vertical spectral ratio of the Scholte waves was also modeled and shown to be very sensitive to the near-surface shear velocity model. Applications of the method include shear-wave statics estimation and geohazard prediction.