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Converting the value into the term needed
for tomography is troublesome.
Etgen (1990) showed that residual
migration *R*_{mig} is the vector sum of residual normal moveout *R*_{nmo},
residual dip moveout *R*_{dmo} and residual zero offset migration
*R*_{zoff} components. What we want to back project in image domain tomography
is the *R*_{nmo} and *R*_{dmo} components.
We can use simple
trigonometry to convert a term to an approximate *R*_{nmo} term through
| |
(9) |

where is the traveltime to the surface
of ray pair starting from at the opening angle .This approximation is not accurate, but has approximately
the correct behavior.

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Stanford Exploration Project

11/11/2002