Amplitude and Phase Accuracy for x-t DMO

Craig J. Beasley

Kirchhoff-summation types of algorithms give an efficient and practical means for accomplishing dip moveout (DMO). In analogy with Kirchhoff migration, space-time (x-t) domain DMO algorithms have been developed by using ray-theory and by transformation of frequency-wavenumber (f-k) domain DMO into the x-t domain. Such approaches to x-t DMO involve approximations that can result in amplitude distortions when compared to f-k DMO. Moreover, phase errors in the form of operator-aliasing noise (which can be easily avoided in the f-k domain) can become a problem in x-t DMO unless special effort is taken. For three-dimensional DMO and prestack processes such as AVO analysis, such errors can become a concern.

Here, we describe a method for deriving x-t DMO from f-k DMO that eliminates these difficulties. Our approach is based upon decomposition of f-k DMO into dip components. This scheme for x-t DMO yields results that, when considering flat events, closely approximate those of f-k DMO and hence, gives accurate phase and amplitude treatment, while retaining the efficiencies inherent in x-t DMO. Further, for dipping events, this new algorithm retains amplitude relationships present in the data prior to application of CMO. In this regard, it is more accurate than f-k CMO which, for dipping events, introduces a decrease in amplitude as a function of offset.

AAPG Search and Discovery Article #91024©1989 AAPG Pacific Section, May 10-12, 1989, Palm Springs, California.