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Source-receiver migration
is based on the concept of
survey sinking.
After each depth propagation step,
the propagated wavefield is equivalent to the data that would
have been recorded if all sources and receivers
were placed at the new depth level.
This task is accomplished by downward continuing
all the source and receiver gathers at each depth step.
Therefore,
the basic downward continuation
is performed by convolving with the
Double Square Root (DSR) equation,
as
| |
(4) |

where the first convolution
downward-continues the
receiver wavefield,
whereas the second convolution downward-continues the
receiver wavefield.
Notice the positive sign on both exponentials in
equation (4).
At each depth level,
the image is extracted from the downward-continued
wavefield by evaluating the wavefield at zero time.
The image-space coordinates and the source-receiver
coordinates are linked by the well-known transformations

The image cube is then computed as
| |
(5) |

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Stanford Exploration Project

11/11/2002