Elastic reflection based waveform inversion in isotropic media

Elastic full waveform inversion (EFWI) of seismic data has been introduced since the inception of FWI and it is supposed to provide a better representation of the subsurface behavior. However, compared with acoustic P-wave assumption, EFWI for P- and S-wave velocities using multi-component data admitted mixed results. FWI is a highly nonlinear problem due to the complex reflectivity of the Earth, and this nonlinearity only increases under the elastic assumption. Reflection waveform inversion (RWI) is designed to admit low wavenumber models with an objective which is to fit the reflection shape, not induce reflections. We propose an elastic RWI that inverts for both the low wavenumber and perturbation components of the P- and S-wave velocities. We utilize an equivalent stress source based on the inverted perturbation. Applications on synthetic isotropic models show that our method can efficiently update the low wavenumber part of the model, but more so, obtain perturbations that can be added to the low wavenumbers for a high resolution output.