# Iteration with prestack data

Series | Investigations in Geophysics |
---|---|

Author | Öz Yilmaz |

DOI | http://dx.doi.org/10.1190/1.9781560801580 |

ISBN | ISBN 978-1-56080-094-1 |

Store | SEG Online Store |

To compare with iterative depth migration applied to zero-offset and CMP-stacked data, we shall examine the performance of iterative depth migration applied to prestack data. Techniques for prestack depth migration itself, however, will be reviewed in the next section. Depth migration of the prestack data using the true model (Model A) shown in Figure 8.2-11 required only one iteration to achieve convergence (Figure 8.2-24).

Next, consider Model D in Figure 8.2-25 in which the salt velocity and the base-salt boundary are incorrectly specified. After the third iteration with the prestack data, we find that convergence is achieved. Nevertheless, the final solution has converged to a velocity-depth model that is different from the true model.

If the initial model contains errors in reflector geometries only, and layer velocities are specified correctly, then convergence using the prestack data to true velocity-depth model is achievable (Figure 8.2-26).

**Figure 8.2-11**Iterative depth migration using the zero-offset section as in Figure 8.2-1 and Model A (same as the true velocity-depth model as in Figure 8.2-1).**Figure 8.2-24**Iterative depth migration using the prestack data as in Figure 8.2-2 and Model A (same as the true velocity-depth model as in Figure 8.2-1).**Figure 8.2-25**Iterative depth migration using the prestack data as in Figure 8.2-2 and Model D that contains errors in salt velocity and base-salt reflector geometry. For comparison, the true velocity-depth model (Model A in Figure 8.2-11) is superimposed on the final velocity-depth model (bottom of left column).**Figure 8.2-26**Iterative depth migration using the prestack data as in Figure 8.2-2 and Model F that contains errors in top-salt and base-salt reflector geometries. For comparison, the true velocity-depth model (Model A in Figure 8.2-11) is superimposed on the final velocity-depth model (bottom of left column).

## See also

- 2-D poststack depth migration
- Image rays and lateral velocity variations
- Time versus depth migration
- Iterative depth migration
- Iteration with zero-offset data
- Iteration with CMP-stacked data
- Iteration in practice