Squeezing dip moveout for depth-variable velocity

In dip-moveout (DMO) processing, velocity variations with depth can be handled approximately by squeezing a constant-velocity DMO operator to narrow its impulse response. This squeezed DMO approximation provides a computationally efficient and reasonably accurate method of DMO correction for depth-variable velocity.DMO is squeezed by two modifications to constant-velocity DMO. One modification is a squeezing function of time that depends only on simple time averages of velocity that are likely to be known before DMO is applied. This squeeze function ensures that squeezed DMO accurately handles moderately steep reflections and can be incorporated with simple time stretching before and after DMO, without any changes to existing constant-velocity DMO methods. The second modification is a constant squeezing factor, which may be used to tune squeezed DMO to better handle steep reflections. This factor requires only trivial changes to constant-velocity DMO methods.Tests with both synthetic and recorded seismic data suggest that squeezed DMO is an effective method for handling velocity variations with depth. These tests also show that the differences between constant-velocity DMO and squeezed DMO can be significant.