NMO correction

 

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Figure 8 Frequency domain NMO correction. On the top left, the input synthetic data. On the top right the NMO-corrected data. On the bottom left inverse NMO-corrected data and on the bottom right the difference of the inverse NMO-corrected and the input data. Clearly the difference is due to NMO stretch

The top left-hand side of Figure  shows a modeled CMP gather consisting of five reflections in a Gaussian noise background. The top right hand-side shows the result of applying NMO correction using the time-variant filtering algorithm described above. The fractional sample interpolation parameter was set to two, meaning that a nearest neighbor interpolation was implicitly performed in the frequency domain to half the sampling interval. Changes in the fractional interpolation parameter would allow for better interpolation at the expense of increased run-time. The result shows a very good correction with very little distortion even for this small interpolation value.

The same algorithm used for forward NMO correction was also applied for inverse NMO correction. The bottom left panel of Figure  shows the inverse-NMO corrected CMP gather. Finally, the bottom right panel of Figure  shows the difference between the original data and the inverse-NMO result. Except for the obvious effect of the NMO-stretch mute, the inverse NMO-corrected CMP is nearly identical to the original CMP.