Conceptually, the simplest approach to migration is also based on the idea of an impulse response. Examples are shown in Figure 2 . Figure 2 Left is a superposition of many hyperbolas. The top of each hyperbola lies along a straight line. That line is like a reflector, but instead of using a continuous line, it is a sequence of points.
Constructive interference gives an apparent reflection off to the side.
Right shows a superposition of semicircles. The bottom of each semicircle lies along a line that could be the line of an observed plane wave. Instead the plane wave is broken into point arrivals, each being interpreted as coming from a semicircular mirror. Adding the mirrors yields a more steeply dipping reflector. Besides the semicircle superposition migration method, there is another migration method that produces a similar result conceptually, but it has more desirable results numerically.