J. Stevens¹ , J. Hanson¹ , D. Salzberg¹ , P.L. Nielsen² , M. Zampolli² , R. Le Bras² , G. Haralabus²

¹Leidos
²CTBTO Preparatory Commission

Abstract:

The IMS Hydroacoustic network consists of 6 Hydrophone stations and 5 T-stations. The T-stations are high-frequency seismic stations (sample rates of 100 Hz) situated on islands or coastal stations and intended primarily to capture signals from in-water explosions. However, while there are numerous recordings of impulsive-like signals at the hydrophone stations, recordings of this type of signal at the T-stations are relatively rare. This is because the conversion of the in-water acoustic signal as it propagates from ocean to land is both complex and characterized by strong attenuation. To improve the understanding of this phase conversion at T-stations, we are performing numerical calculations using the spectral element code SPECFEM2D, modelling the underwater propagation along a path leading towards each T-station and the phase conversion through the ocean/land interface to the seismometer. Environmental information from a variety of sources was gathered to construct the earth and ocean models used in the calculations. The goal of this part of the work is to provide a set of calculated waveforms to complement the limited set of observed waveforms and to assist in the characterization of arrivals from explosion-generated hydroacoustic waves at T-stations.