Elastic full waveform inversion of VSP data from a complex anticline in northern Iraq

We demonstrate an application of isotropic elastic Full-Waveform Inversion (FWI) to a field data set of Vertical Seismic Profiles (VSP) from a structurally complex narrow anticline in Northern Iraq. A practical elastic FWI workflow is developed to invert offset VSP seismic data. Synthetic tests indicate that this approach can give accurate wave speed updates for the target anticlinal structure. We use inverted wave speed models to perform elastic Reverse-Time Migration (RTM) of the data. The RTM results show that the shear wave speed (V_S) image has a higher resolution than the compressional speed (V_P) image for the target structure, owing to the presence of interpretable P-to-S converted waves. The results of the field test show that elastic FWI produces elastic models from which we obtain clear V_S images of the thrust fault of interest.