Suppression of Water-Column Multiples by Combining Components of Ocean-Bottom Seismic Surveys
Methods to suppress water-column multiples by combining components of multicomponent ocean-bottom seismic (OBS) surveys are investigated and tested on both synthetic and field data. The dual-sensor method involves the use of hydrophone and vertical geophone, two motion-sensing components. Since these instruments should record signals with the same polarity for upgoing waves, but with opposite polarity for downgoing waves, the summation of these two, recorded at the same station, with a proper scaling factor, should attenuate the downgoing waves.
Multicomponent wavefield-decomposition techniques evolve naturally from the multicomponent seafloor recording technique, whose essence is combining hydrophone, vertical-geophone and horizontal-geophone components in proper proportions to obtain the upgoing and downgoing wavefields. In order to attenuate the water-column multiples in the recorded OBS data, we can apply this technique to extract the upgoing wavefields on each of components without the downgoing multiples. Then applying a crosscorrelation method, the source-side multiples can be further identified and eliminated from the decomposed upgoing wavefields.