Imaging complex structures with first-arrival traveltimes |

The layer-stripping migration method can be thought of as a hybrid algorithm that incorporates some of the advantages of shot-profile migration with the efficiency of Kirchhoff migration. This is illustrated by Figures 4 through 6.

In shot-profile migration, shots and geophones are alternately downward continued through each depth level. Figure 4 illustrates this for one line of shots or geophones. It is evident that there are many propagation paths from the surface to the image point, therefore multiple arrivals are handled. The computation is performed for all frequencies.

By contrast, first-arrival Kirchhoff migration is performed by summing data over trajectories defined by the propagation paths illustrated in Figure 5. There is only one path linking each surface position to the image point, therefore multiple arrivals are not handled. Although crossing paths are not illustrated here, they can occur.

The layer-stripping method is illustrated in Figure 6. It is a combination of Kirchhoff wave-equation datuming (Berryhill, 1979,1984) and Kirchhoff migration. The computation proceeds as follows:

- Migrate from surface to some depth level .
- Downward continue to depth level .
- Migrate from depth level .
- Downward continue to depth level .
- Migrate from depth level .
- etc...

s-g
Propagation paths from the surface to an image point for shot
profile migration.
Figure 4. | |
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kirch
Propagation paths from the surface to an image point for Kirchhoff downward
continuation.
Figure 5. | |
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datum
Propagation paths from the surface to a depth point for layer-stripping
Kirchhoff downward continuation.
Figure 6. | |
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Imaging complex structures with first-arrival traveltimes |

2013-03-03