Comparison of 1D Conventional and 2D Full Waveform Inversion of Recorded Shallow Seismic Rayleigh Waves

We present a successful application of a 2D elastic full waveform inversion (FWI) to shallow seismic Rayleigh waves. With FWI we are able to reduce the data misfit significantly during the inversion and to find a subsurface model that explains the recorded seismograms well. The reconstructed S-wave velocity model is predominantly depth dependent which is expected for the site under investigation. We observe no significant 2D artefacts although a 1D structure is not enforced by regularization. The field data were acquired on a test site that we chose because of its almost 1D subsurface structure. This gives us the possibility to additionally derive a 1D model by a conventional method that we compare to the 2D model obtained by the FWI. The 1D inversion is done by an inversion of Fourier-Bessel expansion coefficients which requires constant phase velocities along the profile. We observe differences between the 1D and the 2D model although both models produce seismograms with a similar waveform fit of the field data. This shows the ambiguity of the inversion. The 2D model explains the field data slightly better in some details of the waveforms.