Storm microseisms in the 11- to 18-second period range recorded at Palisades and Bermuda are attributed to ocean swell of identical periods in the vicinity of the seacoast near the seismograph station. Evidence is based on travel time, correlation with wave-recorder data, and dispersion of the waves from hurricane Dolly, which remained in deep water when near the Palisades station and passed at a speed greater than the group velocity of ocean swell.
Ground-particle motion is longitudinal, with little or no vertical component.
With some qualifications, the results agree with the classical surf theory of microseism generation. Certainly, the energy is transferred to the earth within the littoral zone.