multiples. Linear coherent noises are also removed by
employing F-K filtering (Fig. 17.20).
NMO correction is applied from a space-variant
velocity field assuming a horizontal reflector and hyperbolic normal moveout algorithm. The NMO is the difference between the travel time for a certain offset (X)
and the vertical (zero-offset) traveltime T(0). Velocities
are interpolated for each CDP. Normal moveout is
applied according to the following formula:
T X
ð Þ ¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi
T 2 ð0Þ þ
X
V
2
"
#
v
u
u
t
(17.5)
Fig. 17.20 (a) A CMP-gather before the F-K filtering: the
primaries dipping up and the multiples dipping down in a
time-distance display. The F-K domain (top, right) shows
energy distributions of both primary and multiples energy,
respectively. (b) The same CMP gather after F-K filtering. The
F-K filtering accepted only primary energy (within polygon) and
filtered out multiples energy (bottom, right)
17 Seismic Exploration
441
employing F-K filtering (Fig. 17.20).
NMO correction is applied from a space-variant
velocity field assuming a horizontal reflector and hyperbolic normal moveout algorithm. The NMO is the difference between the travel time for a certain offset (X)
and the vertical (zero-offset) traveltime T(0). Velocities
are interpolated for each CDP. Normal moveout is
applied according to the following formula:
T X
ð Þ ¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi
T 2 ð0Þ þ
X
V
2
"
#
v
u
u
t
(17.5)
Fig. 17.20 (a) A CMP-gather before the F-K filtering: the
primaries dipping up and the multiples dipping down in a
time-distance display. The F-K domain (top, right) shows
energy distributions of both primary and multiples energy,
respectively. (b) The same CMP gather after F-K filtering. The
F-K filtering accepted only primary energy (within polygon) and
filtered out multiples energy (bottom, right)
17 Seismic Exploration
441