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Stacking to Remove Coherent+Random Noise.

The NMO corrected data in a CMG are now ready to be summed together to form the stacked trace. The MATLAB code for stacking traces in a CMG is given below:
for x=1:nx;
for t0=1:nt;
 trace(t0) = trace(t0) + datanmo(x,t0);
end;
end;

One problem that arises with NMO corrected data is the phenomenon of "stretch", where the far-offset NMO-corrected traces are stretched to a wider frequency. If the stretching is too severe then you just mute such traces prior to stacking.

After stacking the traces in a CMG you get a single stacked trace of your seismic section. Placing all of the stacked traces next to one another provides you with a poststack or ZO seismic section similar to that shown in Figure 1.2. Note that using a stacking velocity tuned to the reflections allows you to reinforce the reflection energy and partly suppress the coherent noise such as surface waves, multiples, etc.. Thus, the ideal ZO section containing only primary reflections is more closely realized.



Gerard Schuster
1998-07-29