Abstract
One of the first steps considered in an imaging project is how to represent the velocity model of the subsurface. Both layered and gridded representations can be used, but if we use layered models, then we must also make some assumptions as to how the velocity changes vertically in each layer, via a compaction gradient function.
In the first part of this paper, we will assess the effect of model representation on an imaging flow and consider the influence of restrictive assumptions on the PreSDM results, including the effects of anisotropy.
In the second part of the paper, we assess the impact of various factors on the amplitude and frequency content of migrated data, and examine the common observation that Pre-stack Kirchhoff depth migrated images sometimes have a lower frequency content than their time-domain counterparts.
We investigate the various factors that influence amplitude and frequency content during migration, with the object of assessing the reasons for potential loss of bandwidth in migrated data, and demonstrate that there is no inherent reason for the bandwidth of Kirchhoff (or depth) migrated data to be worse than other migrated data, and offer recommendations for ensuring optimal frequency content in the processed output image.