We have presented the methodology to built the depth error gather from a 3-D phase-shift downward operator. the 2-D methodology presented in the literature.

The basic difference between the depth error gather built from a 2-D downward operator and the the depth error gather, is a 90 degrees phase-shift of the wavelet in the depth step trace predicted by the 2-D theory. The focusing condition in the focusing depth the depth error panel in 3-D still remains the same as in the 2-D case.

The depth error gather built using a 3-D downward continuation is a 2-D gather of doward continuated zero-offset traces.

The depth error gather built using a 3-D downward continuation operator needs a residual correction in complex velocity models, because the focusing point and the real diffractor position are not along the same path, which in the constant velocity case is a vertical path.

11/11/1997