Ambient seismic noise eikonal tomography for near-surface imaging at Valhall

Conclusions

The ambient seismic field at Valhall contains omnidirectional noise suitable for seismic noise tomography at low frequencies between 0.35 Hz and 1.75 Hz. Scholte-waves traveling along the ocean floor can provide a tomographic image of features in the near surface (between 0 and 105 meters beneath the ocean floor). We have demonstrated that eikonal tomography is an effective tool for studying surface waves at Valhall, even though the gradient estimate sets do not closely resemble Gaussian distributions. This research shows that there is potential for developing a low-cost near-surface monitoring system using passive noise recorded by permanent ocean-bottom arrays.