1.
n. [Geophysics]
A set of numerous closely-spaced
seismic lines that provide a high spatially sampled measure of subsurface
reflectivity. Typical
receiver line
spacing can range from 300 m [1000 ft] to over 600 m [2000 ft], and typical distances between shotpoints and receiver groups is 25 m [82 ft] (offshore and internationally) and 110 ft or 220 ft [34 to 67 m] (onshore USA, using values that are even factors of the 5280 feet in a mile). Bin sizes are commonly 25 m, 110 ft or 220 ft. The resultant data set can be "
cut" in any direction but still display a well sampled
seismic section. The original seismic lines are called in-lines. Lines displayed perpendicular to in-lines are called crosslines. In a properly migrated
3D seismic data set, events are placed in their proper vertical and horizontal positions, providing more accurate subsurface maps than can be constructed on the basis of more widely spaced 2D seismic lines, between which significant
interpolation might be necessary. In particular, 3D seismic data provide detailed information about
fault distribution and subsurface structures. Computer-based
interpretation and display of 3D seismic data allow for more thorough analysis than
2D seismic data.