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.