Common-Azimuth Migration

In order to choose the key migration parameters such as depth step, number of frequencies and especially padding of negative subsurface offsets to accommodate the migration of the multiples, we run some tests using common-azimuth migration. Rather than mapping the non-zero crossline offsets to zero cross-line offset via Azimuth Moveout, AMO, for compuitational simplicity we just windowed the nearest crossline offsets and assigned them to zero crossline offset.

Figure  shows the inline dimensions (CMP and offset) of an SODCIG after common-azimuth migration. Notice that the multiples have been mapped to the negative subsurface offsets and to shallower depths, consistent with the results obtained by Alvarez 2005. Figure  shows the zero subsurface offset cube which shows that the migrated image is good in the inline direction where the sampling was good but is poor in the crossline direction where the CMP sampling was coarse. Notice the multiple that was migrated with roughly twice the crossline dip and in the updip direction.

 

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Figure 10 Inline SODCIG obtained by common-azimuth migration.

 

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Figure 11 Zero subsurface-offset cube of data migrated with common azimuth migration.