Data is acquired over a 3-km grid having adjacent receiver lines staggered in the in-line direction to provide maximum protection against spatial aliasing. For each source line, at least three receiver lines are active throughout the survey, which results in wide azimuth sampling of the subsurface volume. This approach ensures that the entire volume is investigated. One line in each block will be "oversampled" with a 1.0 -1.5 km in-line receiver spacing.