Theory of 3-D angle gathers in wave-equation seismic imaging |

**Sergey Fomel**

I present two methods for constructing angle gathers in 3-D seismic
imaging by downward extrapolation. Angles in angle gathers refer to
the scattering angle at the reflector and provide a natural access
to analyzing migration velocity and amplitudes. In the first method,
angle gathers are extracted at each downward-continuation step by
mapping transformations in constant-depth frequency slices. In the
second method, one extracts angle gathers after applying the imaging
condition by transforming local offset gathers in the depth domain.
The second approach generalizes previously published algorithms for
angle-gather construction in 2-D and common-azimuth imaging.

- Introduction
- Traveltime derivatives and dispersion relationships for a 3-D dipping reflector
- Common-azimuth approximation
- Algorithm I: Angle gathers during downward continuation
- Algorithm II: Post-migration angle gathers
- Discussion
- Conclusions
- Acknowledgments
- Bibliography
- About this document ...

2013-07-26