Fig. 6

Eigenfunctions 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 model