Introduction

Two of the factors that determine the quality of a 3-D post-stack depth migration are the azimuthal isotropy of the impulse response of the algorithm, and the dip handling. Different techniques have been used to maximize the two factors as much as possible Hale (1991); Soubaras (1992). McClellan transformation offers a computationally efficient scheme for depth extrapolation of 3-D seismic data in the frequency domain. The isotropy of the McClellan transformation depends on the accuracy of the approximation used for the ``transformation'' filter; this transformation filter is defined in the wavenumber domain $\vec k$ as $\cos\mid\vec k\mid$.

In our last report Biondi and Palacharla (1993) we suggested a method of improving the accuracy of the transformation filter, without increasing its computational cost. In SEP77 we have shown the impulse responses of the original and the improved filter, and have shown that the improved one has less dispersion than the original McClellan filter. Since the last report, we have further improved the circular response of the McClellan filter. This paper reports our use of a real dataset to study the the differences in the response of the different McClellan filters. The algorithm is implemented on the CM-5 in Fortran-90.