From the equation of *de-migration* (1), it is noticeable
that the observed time *t _{0}* exists only if:

(2) |

The equation (2) above expresses the degree of limitation of the
method with respect to the *V*_{rms} velocity. This means that if the dip of
an initial time migrated surface overflows a certain value imposed by the
value of the *V*_{rms} velocity, the *de-migration* process will fail.

In practice, I observed that for a dipping plane with a *V*_{rms} velocity
equal to 2000m/s, this limitation problem occurs for a dip angle equal to
45 degrees.

11/17/1997