This paper presents an original method for azimuthal residual velocity analysis in a context of wide azimuth acquisition geometry. The 3D analysis is performed on individual Common Image Gather and takes full advantage of the offset vector binning concept which preserves the offset and azimuth information in a consistent manner. The proposed azimuthal residual velocity analysis is based on semblance optimisation by scanning isotropic and anisotropic components of a parabolic elliptical model. The significant imaging improvement that we are seeing with our land data case demonstrates the accuracy of the extracted azimuthal parameters. The azimuthal residual moveout allows seismic events to be stacked constructively when strong azimuthal variations occur.

In this study, an innovative layer stripping approach for FWI specifically adapted to the physics of surface waves is investigated, to mitigate the cycle skipping problem. A combined high-to-low frequency filtering with gradually increasing offset ranges, are applied to observed and calculated data to update gradually deeper layers of the shear velocity model. Successful results for a synthetic data example are presented.

The aim of this study is to determine the advantages and limitations of different misfit functions for an application of Full Waveform Inversion (FWI) to surface waves. The difference-based L2 norm, classically used in FWI and sensitive to both amplitude and phase information, suffers from cycle-skipping and local minima. For slow surface waves propagating in the low velocity near surface, the problem of cycleskipping is even greater due to their small wavelengths. In the absence of low frequencies, convergence may not be possible when starting from a smooth initial mode. Alternative misfit functions applied in various data domains are therefore investigated with the aim of overcoming this issue. Taking the difference-based L2 norm as a basis for comparison, simple synthetic tests are conducted to evaluate a weighted cross-correlation and a singular value decomposition approach as alternative misfit functions, as well as investigating the effect of calculating the residual in different data domains such as the (omega-k), (tau-p) and (omega-p) domains.

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