Marine seismic surveys with enhanced azimuth coverage: Lessons in survey design and acquisition

The azimuth from the source to the receiver in a marine seismic survey acquired with towed streamers is by nature usually close to the sail-line direction. Deviations in this recording azimuth, such as those caused by ocean currents, diminish the quality of the survey results so a substantial effort is made to minimize the damage. Conventional streamer surveys are now called narrow azimuth, or NAZ, even though the same thing was formerly called wide azimuth, and the quality of a “constant” offset (minimal) data set from such a survey has been debated (Padhi and Holley, 1997). There recently have been several surveys designed to increase the multiplicity of azimuths by sailing in multiple directions, called multi-azimuth or MAZ (Hegna and Gaus, 2002); by deploying sources on multiple vessels to widen the effective receiver array, which is known as wide azimuth or WAZ (Sukup, 2002); and by using a combination of both MAZ and WAZ, which is rich azimuth or RAZ (Howard, 2004).