Thematic Set: Velocity model building with wave equation migration: the importance of wide azimuth input, versatile tomography, and migration velocity analysis
F. Audebert, P. Jousselin, B. Duquet and J. Sirgue
Journal name: First Break
Issue: Vol 28, No 4, April 2010 pp. 47 - 54
Info: Article, PDF ( 643.38Kb )
Wave equation migration is suitable for imaging in complex structures. Ideally, its imaging capability should be matched by corresponding velocity model building tools. However, the tool of choice for velocity model building, ray-based tomography, at first sight seems weakly compatible with wave equation migration. To overcome this contradiction we propose several strategies. The first is to convert the wave equation migration image gathers, typically indexed by subsurface offset, into a format appropriate for tomography: local reflection angle or its tangent. In conjunction with this conversion, we employ a datuming procedure to restrict the tomography to a localized domain where it is compatible with the wave equation migration band-limited propagation. A second strategy, more expensive and not yet widely tested, is to replace ray-based tomography with wave-equation-based migration velocity analysis, assuring complete compatibility with the imaging. In all cases, we notice that having wide-azimuth data makes velocity model building easier, as any chosen subsurface azimuth contains specular information.