True 3D High Resolution Imaging for Pre- and Post-Installation of Offshore Infrastructures

Demonstrate the successful application of multiple decimetre-resolution 3D seismic volumes from an exposed, challenging survey location a significant distance offshore. Image subsurface structure in 3D to depths of at least 10 m below seafloor, along with point targets such as boulders or potential UXO. Provide decimetre-accuracy positions for target features in X,Y, and Z. First application of decimetre-resolution 3D seismic imaging for site investigation on an offshore wind site. Despite exposed site, coarse grain sub-surface, and large distance (18 km) from base station, data demonstrate true 3D imaging using a Chirp (1.5 – 13.0 kHz source). Target volumes are small, focused areas (c. 30 x 30 m) or narrow (c. 5 m) corridors primarily for UXO identification around monopoles and along cable routes. Almost 100 % (>95 %) coverage of target areas was obtained in 3 – 4 hours and processed in near real-time. Subsurface stratigraphy is successfully imaged to > 10 m depth below seafloor and multiple point targets are identified. Illustrates the potential of ultra-high-resolutions 3D seismic systems for offshore site survey applications.