Alternative Objective Function for Inversion of Surface Waves in 2D Media

The inversion of surface wave properties contributes to the creation of a near-surface model. In seismic exploration, the proper knowledge of the near surface can improve model building in depth. Most surface wave inversion approaches are based on 1D layered models. We propose here to estimate 2D model parameters by using a full waveform inversion approach with an alternative objective function formulated in the frequency-wavenumber domain. In the novel objective function, oscillations are reduced thanks to the exploitation of the dispersive behavior of surface waves that map into localized propagation modes in the frequency-wavenumber domain. Moreover, spatial windowing is used to allow local comparison of modelled and observed data. For the objective function minimization, a gradient-based approach will be used. We implement the adjoint-state method for an efficient gradient computation. We use simple velocity models to show the reliability of our ormulation to localize anomalies, by comparing the gradients computed with the classical full waveform inversion and the novel approach.