In Figure , the straightforward 3-D interpolation
scheme of SEP-**73** is applied. For each output location,
we select the N (here N=15) nearest neighbors. Each pair of
traces is cross-correlated, and the results are combined to give
an estimate of event coherency as a function of dip. The dip
which gives the maximum coherency is chosen, and the traces
are summed along this trajectory to give a new trace at the
desired output location. Although the stack is over fifteen
traces, the noise has not been attenuated significantly.

In Figure , the stack is weighted by the coherency,
computed as a function of time, measured along the best dip
direction. (Actually semblance is being used here instead of the
generalized coherency of SEP-**73**.)
This weighting supplements the noise suppression
power of the stack and makes a cleaner result. In Figure ,
the median is used instead of the mean, and in Figure ,
both the median and semblance weight are used. This combination
gives the best overall noise suppression.

An example of velocity filtering is shown in Figure . Here we have limited the algorithm to scan over only a certain range of dips; the more steeply dipping event is filtered out. Note that this method does not attempt to deal with the problem of aliased energy.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

11/17/1997