The fold refers to the number of times a particular subsurface point has been sampled. It is equal to the number of traces in the CMP gather and is numerically evaluated byfold=N(numberofgeophones)2nwhere n is the moveup rate in units of geophone spacing. “Moveup rate” is in fact (shot spacing)/(geophone spacing). For example, if geophones are 2 meters apart and shots are employed every 4 meters, then the moveup rate is n=4/2=2. This can be less than one if there are shots set more often than geophone spacing, a practice that is sometimes done in marine seismology, especially ocean bottom profiling.

The observations that stack data quality and acquisition cost both increase with higher CDP fold, and that low fold 3-D out performs high fold 2-D, suggest that an understanding of the noise attenuation mechanism in 3-D stack could lead to lower cost, higher performance 3-D. All the attributes of the BIN are quite important to verify while binning the data.

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