Figure 9. Dip MoveOut (DMO) is a process that is applied after NMO. Since NMO assumes the reflection comes from a horizontal bed, it is picking up only one of many possibilities. For one trace with one reflection event, all possible travel paths have the same length – that is, the distance from source to reflection point to receiver is a constant. The geometrical shape with this property is an ellipse (upper). Some of the original path possibilities are shown in red. NMO reduces travel time based on a horizontal reflector (blue path), while DMO does all the other cases (green). So the action of DMO (lower) is to take the NMO’d event (blue) and broadcast it across several nearby traces (green). Since DMO operates on several traces, it is expensive.