Structurally Consistent Elastic Frequency- Controllable Envelope Inversion for P- and S-Wave Velocity Model Building

Elastic full-waveform inversion (EFWI) can simultaneously build multiple subsurface parameters. However, EFWI faces the ill-posed problem and the multiparameter coupling effects. Building accurate initial P- and S-wave velocity models is crucial for mitigating these issues and ensuring the convergence of EFWI. Yet, limitations of acquisition systems and different sensitivities of P- and S-waves to wavenumber components pose significant challenges in simultaneously building P- and S-wave velocity models with structural consistency. These issues may result in additional iterations, or in some cases, even nonconvergence. Aiming to build accurate long-wavelength velocity models with high structural consistency, a novel structurally consistent elastic frequency-controllable envelope inversion (SC-EFCEI) method is proposed in this article. SC-EFCEI performs multiscale inversion using elastic frequency-controllable envelope data to build long-wavelength models, and additionally introduces structural constraints between different velocity gradients via automatic differentiation (AD) to enforce consistency between the inverted P- and S-wave velocity models. Numerical experiments on the elastic Overthrust model, modified Marmousi2 model, and Chevron 2014 blind dataset verified the effectiveness of the proposed inversion method. The inverted P- and S-wave velocity models both successfully reveal the large-scale features of the velocity model while exhibiting good structural consistency, which can be used as good initial models for EFWI.