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Another difference is that for 3D import you can choose how the seismic cube will be stored within the Geocap project; either in the default new brick format (defaulttype = Seismic Brick Cube) or in the older Vtk format (type = Seismic Cube).
For more information about the SEG-Y format, see the SEG page SEG-Y standard: http://www.seg.org/resources/publications/misc/technical-standards
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