107 4. Near-surface reflection surveying The results obtained by the analysis of the noise profile and the elementary crossspread enabled the acquisition parameters for a 3D survey and processing flow to be defined, to obtain a significant 3D cube in multiple fold (up to 22). The seismic spread was composed of a receiver spread and a source spread. The receiver spread, shown in green, had 2 receiver lines. The receiver line direction is known as the in-line direction. The distance between the receiver lines was 4 m. There were 24 geophones per line. The distance between the geophones was 2 m. The source spread, shown in yellow, was composed of 11 source lines oriented perpendicular to the receiver lines. 11 shots were fired per line. The distance between the shots was 2 m. The distance between the source lines was 4 m. The source lines and the receiver lines were perpendicular. The distance between the receiver spread and the source spread was 4 m. There was no overlap between the source and the receiver spread. Figure 4.13 3D Seismic spread. Due to the geometry of acquisition, the geometric fold was symmetric. Figure 4.14 shows the fold variation, which varied from 0 to 22.
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