ON THE APPLICATION OF TRUE-AMPLITUDE DMO

Constant-velocity, true-amplitude migration to zero offset (MZO) is br oken into two cascaded operations: (a) standard normal moveout (NMO) a nd (b) true-amplitude dip moveout (DMO) corrections. The output of the sequence NMO and true amplitude DMO applied to a constant-offset (GO) section is a simulated zero-offset (ZO) section, in which the geometr ical spreading of primary reflections is the same as would be observed in a real experiment. For constant velocity, 3-D true-amplitude DMO c an be carried out by two-dimensional, in-line Kirchhoff-type stacking. Moreover, both the stacking curve and weights are given analytically by means of simple formulas. For inhomogeneous media, we extend the al gorithm by replacing both in the previous stacking curve and in the we ight formulas the original constant velocity by the NMO velocity at th e output point. At least for mild lateral velocity variations, this ap proach offers an efficient approximation to full MZO as it avoids expe nsive dynamic ray-tracing computations. Synthetic and real seismic dat a examples are presented.