Transfering wave-field checkpoints from disk to the compute engine
is often a bottleneck in Reverse Time Migration (RTM).
The need to create wave-field checkpoints can be eliminated by
running the wave equation backwards and choosing a time
reversible boundary condition. In acoustic propagation, velocity
can be made more and more random within a boundary region. Reflections from
the incoherent boundaries are random in nature and produce minimal
coherent correlations when applying the RTM imaging condition.
In Vertical
Transverse Isotropic (VTI) media, the horizontal and Normal MoveOut (NMO)
velocities can be modified to cause wavefronts to propagate parallel to
the boundary region causing further degradation of coherent signals. Coherent
reflections can be further reduced by decreasing the randomized velocity
within the boundary region.
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