Figure 5

The difference is that, because of its limited aperture, the reflections
originating from the reverse propagation of recorded wavefield will
be limited to a small region of space. As illustrated in the same figure,
the product of the two wavefields has a peculiar **V** shape with
vertex at the reflector. Figure illustrates this concept
for a synthetic shot profile.

Figure 6

Application of this imaging criterion is not straightforward. The following steps can be used to implement the V-stack criterion:

- Define the product function
- Calculate the local semblance of along all directions () around every point
**(**of the profile*x*,*z*)where is the size of the local stacking segment.*x*_{s} - Find the two directions and for which is maximum.
- The estimation of the reflection coefficient is given by

This criterion offers two advantages for the case of non-smooth backgrounds relative to the correlation criterion. It will not have spurious events caused by the overlap of secondary reflections, and the attribute is estimated from wavefield contributions away from the interface, where the interference with other modes is much weaker. These same advantages are present in the next criterion.

11/18/1997