Dmitry Borisov, Associate Research Scholar and Research Geophysicist at Princeton U., presents "Full-waveform inversion using body and surface waves in exploration and near-surface geophysics".

"Full-waveform inversion (FWI) is a data fitting approach to estimate properties of the Earth from seismic data by minimizing the misfit between observed and calculated seismograms. Although many attempts have been made to make the technique more robust, real data inversion is still suffering from the non-linearity of the inverse problem and an insufficient level of physics used to describe the subsurface. In this presentation, I’m going to talk about challenges in exploration and near-surface applications of FWI. Two field examples will be presented. The datasets are dominated by surface waves, which are used to update the shallow part of the shear wavespeed model. For the near-surface study from southern Arizona, where a good initial model is available, we apply a conventional least-squares misfit function to detect voids, such as clandestine tunnels. In the exploration example from onshore Argentina, we use an envelope-based misfit function (Bozdag et al. 2011, Yuan et al. 2015), which diminishes the dependence of oscillating surface waves on the starting model. The recovered shear wave velocity should benefit compressional wavespeed retrieval at later stages of the inversion and a better reconstruction of deeper targets."