A typical poststack processing sequence includes the following steps:
- Deconvolution after stack (field data examples) is usually applied to restore high frequencies attenuated by CMP stacking. It also is often effective in suppressing reverberations and short-period multiples. Figure 1.5-21 shows the CMP stack as in Figure 1.5-20 after spiking deconvolution.
- Although not included in the processing sequence for the Caspian data example in this section, often, time-variant spectral whitening (the problem of nonstationarity) is used to further flatten the spectrum and accounts for the time-variant character of the source waveform.
- Time-variant band-pass filtering (the 1-D Fourier transform) is then used to remove noise at the high- and low-frequency end of the signal spectrum (Figure 1.5-22).
- The basic processing sequence sometimes includes a step for attenuation of random noise uncorrelated from trace to trace (noise and multiple attenuation).
- Finally, some type of display gain is applied to the stacked data (Figure 1.5-23). For true amplitude preservation, time-variant scaling of stacked amplitudes is avoided; instead, a relative amplitude compensation function that is constant from trace to trace is applied. This is a slow time-varying gain function that amplifies weak late reflections without destroying the amplitude relationships from trace to trace that may be caused by subsurface reflectivity.
- CMP sorting
- Velocity analysis
- Normal-moveout correction
- Multiple attenuation
- Dip-moveout correction
- CMP stacking
- Residual statics corrections
- Quality control in processing
- Parsimony in processing