Conditioning the full-waveform inversion gradient to welcome anisotropy

Conditioning the full-waveform inversion gradient to welcome anisotropy

Tariq Alkhalifah, "Conditioning the full-waveform inversion gradient to welcome anisotropy", Geophysics 80 (2015): R111-R122. doi: 10.1190/geo2014-0390.1.
Tariq Alkhalifah
inversion, anisotropy, acoustic
2015
​Multiparameter full-waveform inversion (FWI) suffers from complex nonlinearity in the objective function, compounded by the eventual trade-off between the model parameters. A hierarchical approach based on frequency and arrival time data decimation to maneuver the complex nonlinearity associated with this problem usually falls short in anisotropic media. In place of data decimation, I use a model gradient filter approach to access the parts of the gradient more suitable to combat the potential nonlinearity and parameter trade-off. The filter is based on representing the gradient in the time-lag normalized domain, in which small scattering-angles of the gradient update are initially muted out. The model update hierarchical filtering strategy include applying varying degrees of filtering to the different anisotropic parameter updates, a feature not easily accessible to simple data decimation. Using FWI and reflection-based FWI, when the modeled data are obtained with the single-scattering theory, allows access to additional low model wavenumber components. Combining such access to wavenumbers with scattering-angle filters applied to the individual parameter gradients allows for multiple strategies to avoid complex FWI nonlinearity as well as the parameter trade-off.
(print): 0016-8033 (online): 1942-2156