Multi-component 3D Elastic Full Waveform Inversion Using Surface and Body Waves for Detecting Near Surface Anomalies

We have successfully applied 3D elastic full waveform inversion to detect voids in the near surface (within the first tens of meters). An active source survey with different combinations of sources and several lines of multi-component receivers was acquired over an existing tunnel. We have explained that in our synthetic and field experiments, the low frequency content (below 20 Hz) carries a significant amount of back-scattering surface wave energy from the tunnel, which plays a major role in locating the anomaly. We have shown that the high-resolution three-dimensional velocity models obtained by simultaneously inverting surface and body waves are able detect the tunnel.