next up previous print clean
Next: 3D field data example Up: 2D field data example Previous: 2D field data example

Normal incidence WEMVA

BPGOM.zpc.dsl shows a comparison of normal incidence with prestack wave-equation MVA. The top panel corresponds to normal incidence WEMVA, and the bottom panel corresponds to prestack WEMVA. The general shape of the velocity anomaly is similar, although the vertical resolution of prestack WEMVA is significantly higher. This is a direct result of the increased angular coverage with wavepaths away from the vertical.

 
BPGOM.zpc.dsl
BPGOM.zpc.dsl
Figure 20
A comparison of normal incidence WEMVA (top panel) with prestack WEMVA (bottom panel). Prestack inversion produces anomalies with higher vertical resolution, due to the increased angular coverage.


view burn build edit restore

BPGOM.zpc shows a comparison of three images superimposed on their corresponding velocity model. From top to bottom, the background velocity, the velocity updated by normal incidence WEMVA, and the velocity updated by prestack WEMVA. The updated images have similar characteristics, since the velocity updates are also similar, except for the higher resolution of the prestack inversion. The lesson we can draw from this example is that normal incidence WEMVA is a cheap and convenient alternative to prestack WEMVA, at least for the cases of smooth velocity anomalies. However, if we seek higher vertical resolution, we need to use prestack WEMVA.

 
BPGOM.zpc
BPGOM.zpc
Figure 21
Image and velocity comparison for various types of velocity updates in WEMVA. From top to bottom, the image created with the background velocity (top), the image created with the velocity updated with normal incidence WEMVA (middle), and the image created with the velocity updated with prestack WEMVA (bottom).


view burn build edit restore


next up previous print clean
Next: 3D field data example Up: 2D field data example Previous: 2D field data example
Stanford Exploration Project
11/4/2004