Integrating FWI with Surface-wave Inversion to Enhance Near-surface Modelling in a Shallow-water Setting at Eldfisk

Following a ‘noise becomes signal’ philosophy, we have successfully integrated surface-wave inversion and early-arrival full-waveform inversion on a multicomponent ocean-bottom cable dataset, thus extracting more information from the recorded field data. In the near-surface above the Eldfisk Field, Norwegian North Sea, two perpendicular sets of Pleistocene subglacial tunnel valley systems have been resolved at two depth ranges between the seabed and 300m depth of the updated Vp model by this integrated inversion scheme. This indicates that the integrated near-surface Vp model is of high resolution both laterally and vertically and explains surface-waves and the early arrivals, diving waves, or both. We have demonstrated that surface-wave inversion complements full-waveform inversion by providing a near-surface (0–150 m) Vp model in a depth range where full-waveform inversion techniques typically produce suboptimal results due to null-space issues, vertical resolution limitations and errors in source wavelet, density approximations, multiple modelling, and acoustic assumptions. The combined full-waveform inversion and surface-wave inversion Vp model update in the near-surface significantly flattens the common-image gather events between 0–1000 m and deeper. This confirms the validity of these near-surface updates.