Fig. 6From: Seismic noise between 0.003 Hz and 1.0 Hz and its classificationEigenfunctions of ocean-wave modes for PREM. U is the vertical function and V is the horizontal function of modes. At 0.02 Hz (20.05 mHz), U and V are equal, showing the typical circular particle motion of ocean gravity waves. At 0.003 Hz (left) and 0.010 Hz (middle), they have non-zero values at the ocean bottom. Any topographic deviation from a layered medium can cause scattering and generate Rayleigh waves at the same frequencies. Solid lines are for PREM (elastic model) and dashed lines are for the rigid ocean bottom modelBack to article page