Dip-movement processing for depth-variable velocity. [Correction for variation of velocity with depth]
Dip-moveout correction (DMO) has become commonplace in the seismic processing flow. The goal of DMO processing is to transform the NMO-corrected data to zero-offset, so that the application of zero-offset (poststack) migration is equivalent to full prestack migration of the recorded data. Nearly all DMO implementations assume that the seismic velocity is constant. Usually, this is an acceptable tradeoff because of the tremendous cost savings of DMO and poststack migration versus prestack migration. Where the velocity changes rapidly with depth, however, this constant velocity theory can yield inadequate results. For many areas, such as the Gulf Coast, a velocity function that varies with depth is a reasonable approximation to the true velocity field. Using ray tracing, I find the raypaths from the source and receiver to the reflection point with the given recording time. The time along the corresponding zero-offset ray gives the DMO correction. The relationships between the three rays are expressed by a system of nonlinear equations. By simultaneously solving the equations via Newton-Raphson iteration, I determine the mapping that transforms nonzero-offset data to zero-offset. Unlike previous schemes that approximately handle vertical velocity variation, this method makes no assumptions about the offset, dip, or hyperbolic moveout.
- Research Organization:
- Colorado School of Mines, Golden, CO (United States). Center for Wave Phenomena
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-89ER14079
- OSTI ID:
- 6912912
- Report Number(s):
- DOE/ER/14079-21; CWP--115; ON: DE93004454
- Country of Publication:
- United States
- Language:
- English
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