A wave-extrapolation equation is an expression for the derivative
of a wavefield (usually in the depth *z* direction).
When the wavefield and its derivative are known, extrapolation can proceed
by various numerical representations of

(1) |

- Meet the parabolic wave equation
- Muir square-root expansion
- Dispersion relations
- Depth-variable velocity
- Retardation (frequency domain)
- Lateral velocity variation
- Two velocities
- Splitting diffraction and lens terms
- Time domain
- Upcoming waves

10/31/1997