An angle-domain wavenumber filter for multi-scale full-waveform inversion

The scale length information of velocity perturbations carried by scattered wave is not only dependent on wave frequency but also related to the scattering angle. We introduce a angle-domain wavenumber filter in fullwaveform inversion. Both source and receiver side waves are decomposed into local plane waves, followed by sorting scattering events according to their incidence and scattering angles. The small-angle scatterings are more responsible for large-scale velocity perturbations, while the large scattering angles are related to small-scale perturbations. By controlling scattering angles, we can perform multiscale inversion. Numerical examples reveal, when initial model has large errors, the new inversion method can significantly improve the convergence. The angle-domain wavenumber filter is highly localized, flexible and efficient, and can be combined to most FWI methods.