Applications of 2-D Elastic Full Waveform Inversion to Shallow Seismic Rayleigh Waves

Shallow-seismic Rayleigh waves are attractive for geotechnical site investigations. They exhibit a high signal to noise ratio in field data recordings and have a high sensitivity to the S-wave velocity, an important lithological and geotechnical parameter to characterize the very shallow subsurface. Conventional inversion methods assume local 1D models and invert the dispersion curves of Rayleigh waves. In this work we present a workflow for 2-D elastic FWI that allows for the reconstruction of small-scale lateral velocity models. We apply a geometrical correction and an a priori estimation of the quality factors which used as passive modelling parameters during the multi-parameter FWI. We invert for the seismic velocities and densities, but only the S-wave velocitiy seems to be reliable due to its high sensitivity. Different field data examples demonstrate that realistic small-scale lateral S-wave velocities can be inferred by this approach.