Processing and attenuation of noise in deep seismic-reflection data from the Gulf of Maine

The U.S. Geological Survey deep crustal studies reflection profile across the Gulf of Maine off southeastern New England was affected by three sources of noise: side-scattered noise, multiples, and 20-Hz whale sounds. The special processing most effective in minimizing this noise consisted of a combination of frequency-wavenumber (F-K) filtering, predictive deconvolution, and spectral whitening, each applied in the shot domain (prestack). Application of the F-K filter to remove side-scatter noise in the poststack domain resulted in a much poorer quality profile. The prestack noise suppression processing techniques resulted in a reflection profile with good signal-to-noise ratios and reliable strong reflections, especially at depths equivalent to the lower crust (24–34 km). Certain geologic features, such as a buried rift basin and a crustal fault are resolved much better within the upper crust after this processing. Finite difference migration of these data using realistic velocities produced excellent results. Migration was essential to distinguish between abundant dipping and subhorizontal reflections in the lower crust as well as to show an essentially transparent upper mantle.