Page 470 - Acquisition and Processing of Marine Seismic Data

10.1 NORMAL MOVEOUT TIME 461

FIG. 10.2 (A) A synthetic CDP gather with a reflection hyperbola obtained from a single horizontal layer model, and (B) its
NMO corrected version (upper panel). The ray paths for a reflection recorded at offset x before and after NMO correction are
given in the lower panel. NMO correction removes the offset distances between the source and receivers and reduces all the
arrival times to their corresponding zero-offset time t(0).

Following the NMO correction, all of the 10.1 NORMAL MOVEOUT TIME
traces within a CDP gather are summed up to
produce a single stacked trace, and the process Several expressions have been developed to
is known as stacking. In this section, mathemat- achieve the mathematical expression of normal
ical approaches to the expressions of NMO cor- moveout times of the reflections for earth
rection are depicted, and the effects of different models consisting of horizontally stratified or
agents on the process as well as different stack- dipping layers. These expressions and their con-
ing techniques are discussed. straints can be found in Castle (1994). Here,