![]() |
(1) |
de Bruin et al. (1990), Prucha et al. (1999) and Biondi and Symes (2004)
all provided mechanisms to create reflectivity as a function of
angle based on the focusing of the energy arround zero-offset.
In source-receiver migration, the analysis is naturally done by
analyzing the focusing in the plane.
In shot profile migration
does naturally occur.
Rickett and Sava (2002)
explained how to create subsurface offset for shot profile migration
by cross-correlating the source and receiver fields by various
shifts. As a result subsurface offset volumes can be created
by applying:
![]() |
(2) |
The cost of constructing these sub-surface offset gathers can be significant.
The cost of downward continuing a single shot a single
depth step is dominated by
the FFT cost which grows by () with the size of the data n.
The cost of constructing the subsurface offset gathers is on the order
of nh*n, where nh is the number of subsurface offsets.
Constructing a 2-D subsurface offset gather can be the dominant cost
in shot profile
migration. To construct a 3-D subsurface offset gather as part
of the migration, over 95% of the compute time is common.