Direct building background velocity field by plane-wave multi-source multi-scale full-waveform inversion

Full-waveform inversion (FWI) is one of the most promising inversion methods in geophysics due to its theoretical completeness and high resolution. However, the inversion ability of FWI strongly relies on the accuracy of the initial model and the quality of the low-frequency data. For FWI, it is important to accurately recover low and middle wavenumber components (the background model). In order to invert for the background model, we use a new strategy to compose the plane-wave using reference source points. With the new algorithm, more plane-waves can be composed for a single ray parameter to obtain the background model by plane-wave multi-scale full-waveform inversion (PMFWI) method. By controlling the ray parameter in this method, the low to middle wavenumber components can be recovered in sequence. Composing several plane-waves for a single ray parameter enables the illumination to be significantly improved, even for incomplete data. As only a small number of plane-waves are needed in this method, the computation burden greatly decreases. Analysis of numerical tests also verifies that the proposed inversion strategy is robust, to a certain extent, for high-frequency or noisy data. Application of this method on a modified portion of a SigsBee 2A model illustrates that, combined with conventional FWI, PMFWI has suitable model accuracy, even for coarse initial model data and high-frequency data.