Subsurface offset behaviour in velocity analysis with extended reflectivity images
Version of Record online: 7 NOV 2013
© 2013 Shell Global Solutions International B.V.
Volume 62, Issue 1, pages 17–33, January 2014
How to Cite
Mulder, W.A. (2014), Subsurface offset behaviour in velocity analysis with extended reflectivity images. Geophysical Prospecting, 62: 17–33. doi: 10.1111/1365-2478.12073
- Issue online: 11 DEC 2013
- Version of Record online: 7 NOV 2013
- Manuscript Accepted: MAR 2013
- Manuscript Received: MAY 2012
- Velocity analysis;
- Seismic imaging;
- FD migration
Migration velocity analysis with the constant-density acoustic wave equation can be accomplished by the focusing of extended migration images, obtained by introducing a subsurface shift in the imaging condition. A reflector in a wrong velocity model will show up as a curve in the extended image. In the correct model, it should collapse to a point. The usual approach to obtain a focused image involves a cost functional that penalizes energy in the extended image at non-zero shift. Its minimization by a gradient-based method should then produce the correct velocity model. Here, asymptotic analysis and numerical examples show that this method may be too sensitive to amplitude peaks at large shifts at the wrong depth and to artefacts. A more robust alternative is proposed that can be interpreted as a generalization of stack power and maximizes the energy at zero-subsurface shift. A real-data example is included.