Deep site characterization with full-waveform inversion of SH- and Love-waves induced by large mobile shaker

The ability to reliably image the subsurface is critical for designing and constructing infrastructure, especially in seismically active regions and areas with karstic geologies and underground anomalies. This study explores the application of 2D full-waveform inversion (FWI) of shear horizontal (SH) and Love waves to characterize shear wave velocity (Vs) and density down to a depth of 50 m. The FWI approach employs 2D elastic SH-wave equations for wave simulation and the adjoint-state gradient method with Tikhonov regularization for model updates. The applicability of this FWI approach was first verified using a synthetic four-layer subsurface model representing typical geology of north-central Florida, with soil overlying highly variable limestone. Following promising results from the synthetic study, the approach was applied to a dataset collected at a site near Newberry, Florida using a powerful mobile shaker source (T-Rex). The T-Rex vibroseis truck was instrumental in providing the low-frequency components (down to 5 Hz) essential for deep subsurface characterization. FWI successfully identified an underground anomaly and the depth to bedrock, which were verified through Standard Penetration Testing (SPT).