On the reflectivity-velocity coupling issue in the RFWI method
- Raphael Valensi (Opera) | Reda Baina (Opera)
- Document ID
- Society of Exploration Geophysicists
- SEG International Exposition and Annual Meeting, 15-20 September, San Antonio, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2019. Society of Exploration Geophysicists
- Optimization, Inversion, Full-waveform inversion
- 2 in the last 30 days
- 2 since 2007
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Recently the Reflection Full waveform Inversion method has been proposed as an alternative to classical ray-based velocity model building methods. This method considers a scale separation between the reflectivity and the velocity models. In the original RFWI approach, the reflectivity and the velocity models are inverted by sequentially solving two optimization sub-problems. During the velocity model estimation subproblem, the reflectivity model is keep fixed therefore ignoring reflectivity-velocity coupling effects. This may lead to a slow convergence toward the final velocity model and also generate some in-consistencies between the reflectivity and the velocity model. We propose, here, to reformulate the conventional RFWI approach in order to better account for the coupling between the velocity and reflectivity models. Compared to the conventional RFWI this formulation induces several changes. First, the gradient expression contains the gradient of the conventional RFWI plus an additional term. We show that under particular circumstances, the variable projection method applies allowing to ignore this supplementary gradient term. Another consequence of this formulation is that the reflectivity model has to be re-migrated for every perturbation of the velocity models. Finally, we verify with a synthetic experiment that the reflectivity-velocity consistent RFWI approach has a faster convergence than the conventional approach.
Presentation Date: Monday, September 16, 2019
Session Start Time: 1:50 PM
Presentation Time: 3:55 PM
Presentation Type: Oral
|File Size||944 KB||Number of Pages||5|
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