Editor's note: Öz Yilmaz is presently employed by Anatolian Geophysical in Istanbul, Turkey. Fugen Zhou is presently with Schlumberger Geco-Prakla in Houston, Texas.

An interval velocity field for depth migration derived from Dix conversion of an rms velocity field often is judged to be inaccurate and, consequently, can require an excessive number of iterations to attain a final velocity-depth model with acceptable accuracy. The most likely reason for failing to derive an accurate interval velocity field from Dix conversion is that the input rms velocity field usually is based on velocities estimated from unmigrated data. For instance, a common...

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