Changes

In marine 3-D surveys, the shooting direction (boat track) is considered to be the ''in-line direction'', whereas in land 3-D surveys, the receiver cable is along the in-line direction. The direction that is perpendicular to the in-line direction in a 3-D survey is called the ''cross-line direction''. In contrast to 2-D surveys in which line spacing can be as much as [[length::1 km]], the line spacing in 3-D surveys can be [[length::50 m]] or less. This dense coverage requires an accurate knowledge of shot and receiver locations.

In marine 3-D surveys, the shooting direction (boat track) is considered to be the ''in-line direction'', whereas in land 3-D surveys, the receiver cable is along the in-line direction. The direction that is perpendicular to the in-line direction in a 3-D survey is called the ''cross-line direction''. In contrast to 2-D surveys in which line spacing can be as much as [[length::1 km]], the line spacing in 3-D surveys can be [[length::50 m]] or less. This dense coverage requires an accurate knowledge of shot and receiver locations.

The size of the survey area is dictated by the areal extent of the subsurface target zone and the aperture size required for adequate imaging of that target zone<ref name=pt07r64>Yilmaz, O., 1987 Seismic Data Processing: Society of Exploration Geophysicists, Tulsa, OK, 525 p</ref>. This imaging requirement means that the areal extent of a 3-D survey almost always is larger than the areal extent of the objective. A few hundred thousand to a few hundred million traces normally are collected during a 3-D survey.

The size of the survey area is dictated by the areal extent of the subsurface target zone and the aperture size required for adequate imaging of that target zone.<ref name=pt07r64>Yilmaz, O., 1987 Seismic Data Processing: Society of Exploration Geophysicists, Tulsa, OK, 525 p</ref> This imaging requirement means that the areal extent of a 3-D survey almost always is larger than the areal extent of the objective. A few hundred thousand to a few hundred million traces normally are collected during a 3-D survey.

[[file:three-dimensional-seismic-method_fig1.png|left|thumb|{{figure number|1}}(a) A CMP-stacked section. Copyright: a marine 3-D survey. (b) The corresponding 2-D migrated section. (c) The 3-D migrated section. (Data courtesy of Amoco Europe and West Africa, Inc.]]

[[file:three-dimensional-seismic-method_fig1.png|left|thumb|{{figure number|1}}(a) A CMP-stacked section. Copyright: a marine 3-D survey. (b) The corresponding 2-D migrated section. (c) The 3-D migrated section. (Data courtesy of Amoco Europe and West Africa, Inc.]]