waves and then downward continues
each plane wave independently. Unfortunately, offset plane migration
quickly deteriorates in media that vary from v(z) ().
I chose to instead use another method that has been developed
to do 3-D prestack migration economically,
Common Azimuth Migration.
In CAM each azimuth
is migrated independently, with the assumption
that the source and receivers stay in the same plane while being
downward continued (Figure 2).
() showed that CAM only starts
to loose accuracy when beds dip more than 60 degrees at 45 azimuth
from the recording geometry.
For velocity analysis I felt that this was an acceptable
limitation.
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comaz-down
Figure 2 Geometry of the source and receiver rays for common-azimuth downward continuation. CAM assumes that if the source and receivers are downward continued the downward continued positions will always lay in the same slanted plane. Figure taken from () |  |
