Data from 50 sonobuoys were recorded over the Capel and Faust Basins, 800 km to the east of Australia in water depths 1500-2000 m, during a 2006 seismic survey (GA302) for Geoscience Australia's Big New Oil programme. These data were interpreted and forward modelled by ray-tracing to provide an estimate of P-wave velocities in the upper sedimentary section, and hence constrain estimates of sediment thickness. Also recorded were gravity and magnetic anomaly data which, in conjunction with the very high quality seismic reflection data, provided additional constraints upon the velocity models. Typical ranges in four model layers below water were: 1.9, 2.3-3.0, 3.6-4.7, 5-5.3 km/s. Gravity models based on these results were compared to features identified on depth converted seismic reflection lines and indicate that sediment thickness at densities approximating 2.3 t/m3 may reach 5 km in several localities.
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