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Tutorial: Incorporating near-surface velocity anomalies in pre-stack depth migration models
- Source: First Break, Volume 30, Issue 3, Mar 2012,
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- 01 Mar 2012
Abstract
Unresolved velocity anomalies in the near surface degrade deeper imaging. As a consequence, great care needs to be taken to ensure that all significant near-surface effects have been dealt with before attempting to build the deeper parts of a velocity–depth model. In order to incorporate velocity anomalies into the model, a range of options can be used, depending on whether the geobody geometry alone is discernible, or whether its velocity distribution is also known. Here I describe current industrial practice for building complex near-surface models, which is based on a range of approximate techniques, as well as the more complete solution offered by the emerging technology of waveform inversion. Although building complex nearsurface models is a painstaking process, a suitable near-surface velocity model can usually be obtained.