3D UHRS Depth Velocity Model Building for Offshore Wind Farm Site Characterization

This study presents a depth velocity model building (VMB) workflow applied to 3D Ultra High-Resolution Seismic (UHRS) data for offshore wind farm site characterization. Traditional approaches using 2D lines and time-domain processing offer limited resolution and accuracy. In contrast, this study demonstrates that oil and gas tools like Kirchhoff Pre-Stack Depth Migration (KPSDM) and 3D depth tomography can significantly enhance near-surface imaging. The workflow uses iterative VMB in two model building units (MBUs) to resolve shallow features down to ∼140 m below the seabed, even without borehole velocity logs. Key geological structures like sediment-filled channels and tunnel valleys are identified, and lateral velocity variations of up to 200 m/s are mapped with high precision. The final model’s accuracy is validated against Cone Penetration Test (CPT) data, showing a clear correlation between cone resistance and seismic velocity. These results support improved subsurface interpretation and geotechnical design. Moreover, the derived Vp model contributes valuable low-frequency input for quantitative interpretation and inversion workflows. This case study confirms the effectiveness of 3D UHRS depth imaging for detailed and reliable offshore wind site assessment, suggesting future integration with advanced methods like Full Waveform Inversion (FWI).