p-rock (Probability of Rock) Grids - Caswell Sub-basin, Browse Basin Marine Survey (GA0345/GA0346/TAN1411)

Full 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 p-rock (probability of rock) grids produced from the angular response curves from the multibeam backscatter data. The extraction of angular response curves from the raw Simrad multibeam data was achieved using the multibeam backscatter CMST-GA MB Process v10.10.17.0 toolbox software co-developed by the Centre for Marine Science and Technology (CMST) at Curtin University of Technology and Geoscience Australia (described in Gavrilov et al., 2005a, 2005b; Parnum, 2007). A number of corrections were introduced to the data and the angular response curves were produced as the average response curve within the adopted sliding windows in which port and starboard swath were processed separately as part of the process of the removal of the backscatter angular dependence. Angular backscatter response curves were compared to the reference response of rock/hard bottom (inferred grabs and cores) using the Kolmogorov-Smirnov goodness of fit to estimate the probability (p-value) of rock (p-rock). Finally, the IDW interpolation technique was used to produce a continuous layer of the p-value of hard bottom for each study area.

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