Findings from a previous OSI field exercise have been reviewed and a new discussion panel on resonance seismometry has been launched. There, many seismological techniques have been evaluated regarding their potential to detect underground anomalies such as cavities and rubble zones - typical vestiges of underground nuclear tests. Numerical modeling of the full seismic wavefield has been taken under consideration as an powerful tool to get deeper insight in the causes of observed anomalies and to test and develop techniques for this special target.