Fold and signal to noise ratio

Fold

The number of source/receiver ray paths that have a common mid-point(CMP) in 2D, or the number of CMP's within a given bin for 3D Fold.  In the example above, the bin has '5 fold'.

Full Fold Area

The area of the 3D seismic survey where the maximum fold is achieved for the target offset.  The full fold area does not include migration aperture.

Fold Taper

Areas on the edge of the survey where the fold is 'building-up' to full fold.

Inline Fold Taper

The fold taper in the direction parallel to the receiver lines.

Crossline Fold Taper

The fold taper in the direction perpendicular to the receiver lines.

Signal to Noise Ratio (S/N)

The ratio of Signal to Noise within a seismic program.  The higher the ratio, the easier it is to see the signal.  Notice the CDP gathers 1-4 have a lower S/N ratio when compared to the stacked traces on the left, therefore the Stacked traces have a higher S/N ratio than the CDP gathers.  Often described as the power of the stack

Stack

Is the process of summing seismic traces together to improve the S/N ratio.