Scratching the Surface - Integrating FWI with Surface-wave Inversion to Enhance Shallow-water Near-seabed Modelling

Surface-wave inversion and early-arrival full-waveform inversion can be integrated to extract more information and value from recorded field data. We show how we integrated these technologies and why this integration is beneficial. In fact, these techniques are complementary one to each other; surface waves provide a high-resolution near-seabed model in a depth range where acoustic full-waveform inversion techniques typically produce suboptimal results, and where reflection tomography using the up-going wavefield is typically compromised by a lack of traces that have recorded pre-critical reflections and by multiple and noise contamination at near offsets. The resulting high-resolution P- and S-wave near-seabed velocity models can be obtained after completion of seismic acquisition, and then used for short- to long-wavelength perturbation corrections, for general earth model building, and for geohazard assessment and other geotechnical applications. Obviously, tomography at deeper overburden and reservoir depth range, as well as PSDM imaging quality of the reservoir targets is expected to benefit from the correct velocity modelling of small-scale and complex structural and stratigraphic features in the near surface. For shallow hazard assessment, the integrated near-surface model can be used as interpretation product, and would improve mirror migration of the down-going wavefield.