How moderate sea states can generate loud seismic noise in the deep ocean

The location of oceanic sources of the micrometric ground displacement recorded at land stations in the 0.1-0.3 Hz frequency band (double frequency microseisms) is still poorly known. Here we use one particularly strong noise event in the Pacific to show that small swells from two distant storms can be a strong deep-water source of seismic noise, dominating temporarily the signals recorded at coastal seismic stations. Our interpretation is based on the analysis of noise polarization recorded all around the source, and the good fit achieved for this event and year-round between observed and modeled seismic data. The model further suggests that this is a typical source of these infrequent loud noise bursts, which supports previous inconclusive evidences of the importance of such sources. This new knowledge based on both modeling and observations will expand today's limits on the use of noise for climate studies and seismic imaging. Citation: Obrebski, M.J., F. Ardhuin, E. Stutzmann, and M. Schimmel (2012), How moderate sea states can generate loud seismic noise in the deep ocean, Geophys. Res. Lett., 39, L11601, doi: 10.1029/2012GL051896.