A novel envelope inversion method with frequency selection mechanism

An accurate initial model is crucial for full waveform inversion (FWI). Envelope inversion (EI) is a powerful method for recovering long-wavelength components of the subsurface structure and building an initial model for FWI. In this paper, we improve EI by embedding a frequency selection mechanism into it. We propose a frequency selected envelope operator (FSEO) and compare its feature with envelope operator (EO) by applying them to the waveform. We develop a new inversion method by defining a misfit function based on the FSEO and deriving the corresponding gradient operator. Numerical results using synthetic data from the Marmousi model demonstrate that compared with EI, our proposed method is less sensitive to the initial model and can build an initial model with more accurate long-wavelength components that then significantly benefit the final results of conventional FWI.