Seabed Shear-Wave Velocity Estimation from Dispersion Curves of Love Waves

This paper applies a linearized inversion to estimate seabed shear-wave velocity profiles using dispersion curves of Love waves, and compares the inversion results from Love- and Scholte-wave dispersion curves to obtain information on shear-wave anisotropy in the shallow sediments. Both the Love and Scholte waves were generated by an in-line polarized shear-wave source and recorded by a multicomponent ocean-bottom cable in an experiment in the North Sea. The dispersion curves of the Love and Scholte waves are extracted using three time-frequency analysis methods. Three dispersion modes for both the Love and Scholte waves are well separated and extracted. The shear-wave velocity profiles of the seabed sediments are estimated by inverting two and three modes of the Love waves, respectively. Compared with nonlinear inversion methods, the linearized inversion method is extremely fast since it needs only few iterations when a reasonable initial shear-velocity profile is used. The inversion results of the horizontal and vertical polarized shear-wave velocity profiles indicate a weak shear-wave anisotropy which correlates fairly well with the clay content in the shallow sediments and the in situ stress conditions estimated for the area.