Suppressing multiples by NMO differences
Jump to navigation
Jump to search
![]() | |
Series | Geophysical References Series |
---|---|
Title | Problems in Exploration Seismology and their Solutions |
Author | Lloyd P. Geldart and Robert E. Sheriff |
Chapter | 6 |
Pages | 181 - 220 |
DOI | http://dx.doi.org/10.1190/1.9781560801733 |
ISBN | ISBN 9781560801153 |
Store | SEG Online Store |
Problem 6.11
A primary and a multiple each arrive at 0.600 s at ; their stacking velocities are 1800 and 1500 m/s, respectively. Calculate the residual NMO (after NMO correction for the primary velocity) for offsets of 300 , where . What is the shortest offset that will give good multiple suppression for a wavelet with a 50-ms dominant period?
Solution
The distance to the primary reflector is and to the reflector responsible for the multiple, assuming it is simply a double bounce, is . NMO is given by equation (4.1c), . We obtain the following values for the moveouts:
Offset | 300 m | 600 m | 900 m |
Primary NMO | 0.023 s | 0.093 s | 0.208 s |
Multiple NMO | 0.033 s | 0.133 s | 0.300 s |
NMO Difference | 0.010 s | 0.040 s | 0.092 s |
Multiple suppression should be maximum when the NMO difference approximates half the wavelet period so that some of the traces are out-of-phase, which is achieved at offset where
Continue reading
Previous section | Next section |
---|---|
Differential moveout between primary and multiple | Distinguishing horizontal/vertical discontinuities |
Previous chapter | Next chapter |
Geometry of seismic waves | Characteristics of seismic events |
Also in this chapter
- Characteristics of different types of events and noise
- Horizontal resolution
- Reflection and refraction laws and Fermat’s principle
- Effect of reflector curvature on a plane wave
- Diffraction traveltime curves
- Amplitude variation with offset for seafloor multiples
- Ghost amplitude and energy
- Directivity of a source plus its ghost
- Directivity of a harmonic source plus ghost
- Differential moveout between primary and multiple
- Suppressing multiples by NMO differences
- Distinguishing horizontal/vertical discontinuities
- Identification of events
- Traveltime curves for various events
- Reflections/diffractions from refractor terminations
- Refractions and refraction multiples
- Destructive and constructive interference for a wedge
- Dependence of resolvable limit on frequency
- Vertical resolution
- Causes of high-frequency losses
- Ricker wavelet relations
- Improvement of signal/noise ratio by stacking