The numerical experiment uses a highly realistic velocity model
composed of stratigraphically plausible succession of reflectors
superimposed over a linearly increasing background velocity. Figure
displays some properties of the velocity model.
Figure 1Left: Background velocity;
Right: Histogram of velocity deviation from the background, in
percentages, for a random number of samples in a certain region of
The velocity variations are sufficiently abrupt to cause
massive multiple internal reflections when modeled with a two-way
propagation algorithm. Figure shows both multiple-free
data created with a one-way algorithm (split-step with three reference
velocities) and multiple-affected data created with a
finite-difference algorithm. Vertical streaks of high-amplitude
focusing are visible, especially in the multiple-free panel.
Figure 2 Zero-offset data. Left: without multiples;
Right: with multiples.