Jingrui Luo

Seismic envelope inversion: reduction of local minima and noise resistance

Waveform inversion met severe challenge in retrieving long-wavelength background structure. We have proposed to use envelope inversion to recover the large-scale component of the model. Using the large-scale background recovered by envelope inversion as new starting model, we can get much better result than the conventional full waveform inversion. By comparing the configurations of the misfit functional between the envelope inversion and the conventional waveform inversion, we show that envelope inversion can greatly reduce the local minimum problem. The combination of envelope inversion and waveform inversion can deliver more faithful and accurate final result with almost no extra computation cost compared to the conventional full waveform inversion. We also tested the noise resistance ability of envelope inversion to Gaussian noise and seismic interference noise. The results showed that envelope inversion is insensitive to Gaussian noise and, to a certain extent, insensitive to seismic interference noise. This indicates the robustness of this method and its potential use for noisy data.

Elastic Envelope Inversion

We developed the elastic envelope inversion method. The envelope of the wavefields carries ultra low frequency information which can be used to recover the large-scale component of the model, and the initial model dependence of waveform inversion can be reduced. We derived the misfit function and the corresponding gradient operator for elastic envelope inversion. Numerical tests using synthetic data for the Marmousi II model proved the validity and feasibility of the proposed approach. The inverted p-wave velocity and s-wave velocity from the combined (EI WI) envelope inversion plus waveform inversion indicated that it can deliver much improved results compared with regular elastic full waveform inversion.