Normalized nonzero-lag crosscorrelation elastic full waveform inversion

Normalized nonzero-lag crosscorrelation elastic full waveform inversion

Zhendong Zhang, Tariq Alkhalifah, Zedong Wu, Yike Liu, Bin He, and Juwon Oh, "Normalized nonzero-lag crosscorrelation elastic full waveform inversion​", Geophysics 84 (2019): R1-R10. doi: 10.1190/geo2018-0082.1​
Zhendong Zhang, Tariq Alkhalifah, Zedong Wu, Yike Liu, Bin He, Juwon Oh
elastic FWI
2019
​Full Waveform Inversion (FWI) is an attractive technique due to its ability to build high-resolution velocity models. Conventional amplitude-matching FWI approaches remain challenging because the simplified computational physics used does not fully represent all wave phenomena in the Earth. Since the Earth is attenuating, a sample by sample fitting of the amplitude may not be feasible in practice. We propose a normalized nonzero-lag crosscorrelataion-based elastic FWI algorithm to maximize the similarity of the calculated and observed data. We use the first-order elastic wave equation to simulate the propagation of seismic waves in the Earth. Our proposed objective function emphasizes the matching of the phases of the events in the calculated and observed data, and thus is more immune to inaccuracies in the initial model and the difference between the true and modeled physics. The normalization term can compensate the energy loss in the far offsets because of geometrical spreading and avoid a bias in estimation toward extreme values in the observed data. We introduce a polynomial-type weighting function and suggest an approach to determine the optimal time lag. We use a synthetic elastic Marmousi model and the BigSky field data set to verify the effectiveness of the proposed method. To suppress the short-wavelength artifacts in the estimated S-wave velocity and noise in the field data, we apply a Laplacian regularization and a total variation (TV) constraint on the synthetic and field data examples, respectively.
(print): 0016-8033 (online): 1942-2156