The depth conversion of seismic reflection records has been the subject of many papers, particularly where faults or other geologic features are present. The common-depth-point (CDP) stacked seismic sections with large spread lengths of the order of 2 km have resulted in different interpretation problems. Al-Chalabi (1979) considered the effect on stacking velocities of subsurface inhomogeneities where different rays in the CDP gather do not penetrate the same type of earth column. He showed that small time delays of 10 msec produce steps in the hyperbolic offset distance-time curve of the CDP gather and produce stacking velocity variations of the order of ten percent. Levin (1973) considered a time delay in only one ray of the CDP gather and its effect on both stacking velocity and the zero-offset time T0. This paper models the effect of near-surface faults on the zero-offset time T0 of deeper layers as determined by the CDP method. This is particularly important since the zero-offset time is plotted on the processed final record.

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