Page 501 - Acquisition and Processing of Marine Seismic Data

492 10. NORMAL MOVEOUT CORRECTION AND STACKING

not the case for the last CDPs, since they are in Fig. 10.35C, the last three CDPs consist of
composed of only near offset traces, which do traces shown by the green and blue ray paths.
not stretch after NMO correction. All traces in CDP numbers 10, 11, and 12 are
This situation is schematically illustrated in recorded at the nearest three receivers, and
Fig. 10.35. Let’s consider a seismic line with are composed of only near offset traces.
only four shots recorded at six receivers. At Fig. 10.35D and E show real data examples from
the start-of-line in Fig. 10.35B, the first three the very first and very last CDPs of a small-
CDPs consist of traces shown by the black spread marine seismic line with a 693-m maxi-
and red ray paths. All traces in CDP numbers mum offset, which indicates that trace offsets
1, 2, and 3 are recorded at the farthest three change between 662 and 693 m for the first
receivers, and are composed of only far offset six CDPs, while they vary from 100 to 131 m
traces. On the other hand, at the end-of-line for the last six CDPs.