Shipboard Multibeam Backscatter Grids - Caswell Sub-basin, Browse Basin Marine Survey (GA0345/GA0346/TAN1411)

Brief description

Geoscience Australia (GA) conducted a marine survey (GA0345/GA0346/TAN1411) of the north-eastern Browse Basin (Caswell Sub-basin) between 9 October and 9 November 2014 to acquire seabed and shallow geological information to support an assessment of the CO2 storage potential of the basin. The survey, undertaken as part of the Department of Industry and Science's National CO2 Infrastructure Plan (NCIP), aimed to identify and characterise indicators of natural hydrocarbon or fluid seepage that may indicate compromised seal integrity in the region. The survey was conducted in three legs aboard the New Zealand research vessel RV Tangaroa, and included scientists and technical staff from GA, the NZ National Institute of Water and Atmospheric Research Ltd. (NIWA) and Fugro Survey Pty Ltd. Shipboard data (survey ID GA0345) collected included multibeam sonar bathymetry and backscatter over 12 areas (A1, A2, A3, A4, A6b, A7, A8, B1, C1, C2b, F1, M1) totalling 455 km2 in water depths ranging from 90 - 430 m, and 611 km of sub-bottom profile lines. Seabed samples were collected from 48 stations and included 99 Smith-McIntyre grabs and 41 piston cores. An Autonomous Underwater Vehicle (AUV) (survey ID GA0346) collected higher-resolution multibeam sonar bathymetry and backscatter data, totalling 7.7 km2, along with 71 line km of side scan sonar, underwater camera and sub-bottom profile data. Twenty two Remotely Operated Vehicle (ROV) missions collected 31 hours of underwater video, 657 still images, eight grabs and one core. This catalogue entry refers to the shipboard multibeam backscatter grids produced for the twelve survey areas (Areas A1, A2, A3, A4, A6b, A7, A8, B1, C1, C2b, F1b and M1; 455 km2).

Lineage

Maintenance and Update Frequency: asNeeded

Statement: The backscatter data were processed using CMST-GA MB Process v12.05.07.0 (x64) toolbox software. The fully processed backscatter strengths were corrected for transmission loss and insonification area. The process within the toolbox also involved removal of the system transmission loss, removal of the system model, calculation of the incidence angle and removal of the angular dependence. The grid values are basically the average values of the processed backscatter point data within each grid cell of predefined size, normalised to the backscatter strength at an angle of 25 degrees.