Datuming

The regular cube was then datumed to just above the water-bottom to avoid spending precious migration time on downward continuation through the water layer. Figure  shows a comparison of one CMP 3D gather before (left) and after datuming (right). Notice that datuming not only saves time but also allows a significant reduction of the data because the offsets decrease as the recording surface is ``moved'' closer to the reflectors, making the positions of sources and receivers closer. Notice also that the holes in both offsets and CMPs have been healed by the propagation.

 

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Figure 9 Comparison of a 3D CMP gather before (left) and after datuming (right).