Acoustic target-level full-waveform inversion: Applied to ocean-bottom seismic data

Full-waveform inversion approaches aim to recover the subsurface model parameters with high resolution and accuracy. However, mainly due to its non-linear nature and high computational cost, the inversion process may result in an estimated model with low resolution and high uncertainty. Mitigating the non-linearity and applying appropriate pre-conditioning on the gradient of its objective function, helps to drive the full-waveform inversion to get realistic subsurface models. We present an application of the acoustic target-level fullwaveform inversion method for ocean bottom seismic data. The objective function of this method is built from fitting the observed with the modeled upgoing wavefields just above the target area. Along a target level beneath the overburden, the upgoing wavefields are less affected by overburden distortions. Therefore, the objective function may have a lower degree of nonlinearity, and its gradient can require less preconditioning to update the model in the right direction. Using a synthetic model, we show numerically that, under some conditions, target-level full-waveform inversion applied to ocean bottom seismic data can yield an inverted model with better accuracy than the conventional full-waveform inversion.