Geoscience Reference
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Fig. 2.29 Bin expansion. Flexi-binning is used so as to ensure that each bin has a regular
distribution of traces with the full range of offsets. Three examples are illustrated here. Bin A is
expanded for a near offset trace with relatively small expansion. Bin B is seeking a trace with larger
offset. The bin expansion is greater and has thrown up three possibilities. The trace closest to the
bin centre is the one that gets borrowed. Bin C already has a far offset trace and no bin expansion is
required. The red trace will end up being used by both bin A and bin D. After binning, the traces
are treated as though they came from the centre of the bin though it is normal to retain and use the
absolute offset information for later processing.
furthest offsets may be non-uniformly distributed with some bins having two or more
traces with a similar offset while others have none. To make the distribution of offsets
more uniform a process called flexi-binning is used. Here the bins are extended by fixed
amounts (generally) in the crossline direction, perhaps by as much as 50% either side
(fig. 2.29) . If no trace within a certain offset range is found within the original bin, then
a trace within the extended bin is used as though it falls in the original bin. If more than
one trace within an offset range is found, then it is usual for the trace closest to the bin
centre to be used. The bin expansion is normally small for the near offsets, since the
cable position is better controlled close to the boat, and grows with increasing offset.
Note that the process as described just copies a trace from one location to another. This
copying means that there may be small static shifts between traces within a binned
CDP, since one trace may come from the extreme top edge of a flexed bin and the
next offset may come from the bottom edge. Figure 2.30 shows a binned gather with
 
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