3D seismic-derived bathymetry: a quantitative comparison with multibeam data

This study compares bathymetry extracted from 3D seismic data at two Australian study sites of differing morphological complexities to two sources of collocated multibeam data: 50-m and 5-m multibeam digital bathymetric models (DBMs). Seafloor horizons are extracted from the 3D seismic data and converted to depth using sound velocity profiles collected during seismic acquisition. The resulting seismic-derived DBMs are independent of the multibeam DBMs and are shown to be highly comparable. For the morphologically simple site, the seismic-derived DBM was within ± 2% of the multibeam DBMs and, at 2σ, 95% of differences are in the range - 1.22 to 0.10% (- 1.02 to 0.48%) for the 50-m (5-m) multibeam DBM. For the morphologically complex site, > 80% (> 99%) of seismic-derived depths were within ± 2% (± 5%) of multibeam DBMs. At 2σ, 94% of differences are in the range - 3.48 to 1.69% (- 2.73% to 2.44%) for the 50-m (5-m) multibeam DBM. Increasing morphological complexity and slope angle were the most important factors affecting DBM comparisons, with seismic-derived depths typically underestimated in canyon thalwegs. Despite these differences, the higher data density, multichannel stacking and migration of the 3D seismic data resulted in seismic-derived DBMs with high resolution and improved feature relief and clarity when compared to multibeam DBMs for the conditions in this study (depths of 120 - 1900m), particularly for morphological features such as individual rills and gullies. This method has the potential to expand the spatial coverage of high-resolution DBMs, for example, in Australia, by over 150,000km2.