Near-surface Scholte wave velocities at Ekofisk from short noise recordings by seismic noise gradiometry

We propose a new approach for imaging the subsurface using a stochastic wavefield of interface waves present in the ambient seismic field. Unlike seismic interferometry, our technique does not rely on cross correlations to obtain the Green's function between two seismic receivers. Rather, it relies on the local measurements of phase velocity obtained directly from the ratio between second-order temporal and spatial derivatives of the wavefield. We process 10 min of ambient seismic noise recording made using a large and dense array installed over Ekofisk. We image a subsidence-induced geomechanical imprint on the Scholte wave phase velocities in the near surface. This resulting phase velocity pattern is verified by comparison to results from a seismic-noise cross-correlation tomography.