Abstract
A three‐dimensional (3-D) wave‐equation migration program is used to migrate swath data (swath data are here defined as a very narrow 3-D survey consisting of approximately ten seismic lines and having a width of about 500 m). Three‐dimensionally migrated swath data give an accurate 3-D image of the subsurface and have a higher signal‐to‐noise ratio than 2-D data. These advantages are gained at the expense of lateral resolution in the crossline direction and less extensive 3-D subsurface coverage. Since swaths are on the order of one‐tenth the size of a normal 3-D survey, the costs of gathering and processing swath data are about 10 percent those of a conventional 3-D survey. Thus 3-D migrated swath surveys are a practical means of producing 3-D images in areas where the expense of conventional 3-D surveys is not justified. Following 3-D wave‐equation migration, inlines from the swath data are geologically interpretable. However, crosslines from the swath data are dominated by migration artifacts (often called migration smiles), making them uninterpretable. Relatively high‐amplitude portions of these migration smiles indicate where the data were accurately migrated. These facts lead to a two‐step method of interpreting 3-D migrated swath data. First the inlines are interpreted geologically, then the accuracy of that interpretation is verified by tying it to the crossline data.
Published Version
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