Changes

==Vertical seismic profiles==

==Vertical seismic profiles==

A vertical seismic profile (VSP) is recorded in essentially the same way as a checkshot survey<ref name=pt07r2>Balch, A. H., Lee, M. W., eds., 1984, Vertical seismic profiling—technique, applications, and case histories: Boston, MA, IHRDC, 488 p.</ref>; <ref name=pt07r17>Hardage, B. A., 1985, Vertical seismic profiling, Part A— principles, 2nd ed.: Oxford, U., K., Pergamon Press, 509 p.</ref>. The major difference between a VSP and a checkshot survey is that VSP data are recorded at much smaller spatial sampling intervals than checkshots. While a receiver may be moved a vertical distance of 200 to [[depth::1000 ft]] (61 to 305 m) between checkshot levels, it should be moved no more than 50 to [[length::100 ft]] (15 to 30 m) when recording a VSP. Specifically, the vertical distance between successive VSP traces should not exceed one-half of λ_min, where λ_min is the shortest wavelength contained in the recorded VSP wavefield.

A vertical seismic profile (VSP) is recorded in essentially the same way as a checkshot survey<ref name=pt07r2>Balch, A. H., Lee, M. W., eds., 1984, Vertical seismic profiling—technique, applications, and case histories: Boston, MA, IHRDC, 488 p.</ref> <ref name=pt07r17>Hardage, B. A., 1985, Vertical seismic profiling, Part A— principles, 2nd ed.: Oxford, U., K., Pergamon Press, 509 p.</ref>. The major difference between a VSP and a checkshot survey is that VSP data are recorded at much smaller spatial sampling intervals than checkshots. While a receiver may be moved a vertical distance of 200 to [[depth::1000 ft]] (61 to 305 m) between checkshot levels, it should be moved no more than 50 to [[length::100 ft]] (15 to 30 m) when recording a VSP. Specifically, the vertical distance between successive VSP traces should not exceed one-half of λ_min, where λ_min is the shortest wavelength contained in the recorded VSP wavefield.

When a seismic wave field is recorded with this small spatial sampling interval, several processing techniques can be used to separate the down-going and up-going wave fields. Once the up-going wave field is isolated from the more dominant down-going wave field, the up-going reflection events can be properly analyzed and interpreted and used to produce improved imagery of the subsurface.

When a seismic wave field is recorded with this small spatial sampling interval, several processing techniques can be used to separate the down-going and up-going wave fields. Once the up-going wave field is isolated from the more dominant down-going wave field, the up-going reflection events can be properly analyzed and interpreted and used to produce improved imagery of the subsurface.