Inversion of Elastic Properties of Stratified Layered Media using EDWI - Elastic Direct Waveform Inversion

Conventional gradient-based elastic full waveform inversion methods encounter challenges associated with local minima and trade-offs in multi-parameter inversion. To address these issues, we developed a new method, called the elastic Direct Waveform Inversion (eDWI) scheme. By explicitly enforcing the time-space causality of the wavefield, our eDWI converts, without loss of information, the global iterative non-linear inversion problem into a sequence of localized recursive inversions performed from shallow to deep depths. We tested our method on two numerical examples for stratified layered elastic media with both a plane-wave source and a point source. We use the Stiffness Matrix Method to decompose and extrapolate wavefields into up/down-going P and S wavefields, and employ specific P-to-P and P-to-S reflection events for the localized recursive inversion. Our numerical examples have shown that our new approach does not need a global initial model, avoids local minima and parameter coupling issues. It automatically uses multiples, and maintains efficacy even without low-frequency content in the recorded seismic data. Our new inversion approach may find a wide range of imaging and sensing applications using seismic and other wave