Wraparound

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Seismic Data Analysis
Seismic-data-analysis.jpg
Series Investigations in Geophysics
Author Öz Yilmaz
DOI http://dx.doi.org/10.1190/1.9781560801580
ISBN ISBN 978-1-56080-094-1
Store SEG Online Store


Wraparound is the effect of finite data length in time and space on a migration algorithm implemented in the Fourier transform domain. A migration algorithm implemented in the time-space domain does not suffer from wraparound effect. But a migration algorithm implemented in the frequency-space domain suffers from wraparound along the time axis. Similarly, a migration algorithm implemented in the frequency-wavenumber domain suffers from wraparound effects both along the time and space axes.

Figure 4.5-22 shows a zero-offset section that contains a diffraction hyperbola and its migration using frequency-wavenumber migration based on the phase-shift method. When plotted with a very high display gain, we observe the energy in the migrated section bouncing off the edges of the section both in the time and space directions.

A field data example of the wraparound effect on frequency-wavenumber migration is shown in Figure 4.5-23. This is the same section as in Figure 4.2-15b, except that it has been displayed using a very high gain. The energy above the water bottom is associated with the wraparound effect in the time and space directions. The wraparound noise actually exists within the image portion of the section, also. A way to reduce the wraparound effect is to pad the data with zeros along the axis of Fourier transformation. For frequency-space migration, data must be padded along the time axis; and for frequency-wavenumber migration, data must be padded along both the time and space axes.

A field data example of the wraparound effect on frequency-space migration is shown in Figure 4.5-24. This is the same section as in Figure 4.4-11d, except that it has been displayed using a very high gain. The energy above the water bottom is associated with the wraparound effect in the time direction.

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Wraparound
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