W.L. Chapman, 1983. "Erosional Unconformity, River Channel", Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces, A. W. Bally
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Figure 1 shows a conventional "Vibroseis" data acquisition effort across a stratigraphic channel sand. A 58-12 Hz sweep was used with the data recorded for 24-fold stack. The data have been processed to maximally emphasize the objective zone at a depth of 4,700 ft (1,432 m). This objective depth is marked on the right side of the seismic section at about 0.9 seconds with a label identifying the known sand channel location. Figure 2 shows high frequency data recorded along the same line. Again, the zone of interest is shaded gray in Figure 3, a marked version of 2, at a depth of 4,700 ft (1,432 m). The data was recorded with a 90-25 Hz sweep, and excellent 909 Hz penetration was obtained at the objective depth. The increased frequency content is apparent and provides adequate resolution to map 30 ft (9 m) sands. The limits of the sand channel are easily seen on the high-frequency data, whereas extensive interpretation is required to locate the channel on the conventional data.