HR: 08:30h
AN: S11D-03    [Abstracts]
TI: The origin of deep ocean microseisms in the North Atlantic Ocean
AU: * Kedar, S
EM: Sharon.Kedar@jpl.nasa.gov
AF: Jet Propulsion Laboratory - California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Longuet-Higgins, M
EM: mlonguet@ucsd.edu
AF: Institute for Nonlinear Science - University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0402, United States
AU: Webb, F
EM: Frank.H.Webb@jpl.nasa.gov
AF: Jet Propulsion Laboratory - California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Graham, N
EM: ngraham@hrc-lab.org
AF: Hydrologic Research Center, 12780 High Bluff Drive, #250, San Diego, CA 92130-3017, United States
AU: Clayton, R
EM: clay@gps.caltech.edu
AF: Seismological Laboratory, California Institute of Technology, 1200 E. California Blvd., MS 252-21, Pasadena, CA 91125-2100, United States
AU: Jones, C
EM: Cathleen.E.Jones@jpl.nasa.gov
AF: Jet Propulsion Laboratory - California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AB: Oceanic microseisms are small oscillations of the ground, in the frequency-range 0.05-0.3 Hz, associated with the occurrence of energetic ocean waves of half the corresponding frequency. In 1950 Longuet-Higgins suggested in a classical theoretical paper that microseisms originate from the interaction between oppositely- traveling components in the ocean wave spectrum. The theory provided an estimate of the magnitude of the corresponding microseisms in a compressible ocean, which has never been tested quantitatively. In this presentation we report explicit calculations of microseisms amplitudes making use of hindcast ocean wave spectra from the North Atlantic Ocean, and comparison of the calculations to seismic data collected at stations in North America, Greenland, and Iceland. We find that a particularly energetic source area stretches from the Labrador Sea to a region south of Iceland, where climatological conditions are conducive to generating oppositely traveling waves of same period, and where the ocean depth corresponds to an "organ-pipe" resonance of the compression waves generated by the opposing wave-wave interaction, as predicted by the theory. It is demonstrated that deep ocean nonlinear wave-wave interactions are sufficiently energetic to account for the observed seismic amplitudes in North America, Greenland and Iceland.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3025 Marine seismics (0935, 7294)
DE: 7200 SEISMOLOGY
DE: 7255 Surface waves and free oscillations
SC: Seismology [S]
MN: 2007 Fall Meeting