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We have made a step forward in developing a methodology for processing, interpreting and presenting near-vertical reflection, wide-angle reflection and refraction seismic data and velocity information derived from these data sets within a unified approach. Wide-angle reflection and refraction data that we used to supplement conventional CDP (near-vertical reflection) data were recorded by ocean-bottom (OBS) seismographs on the Australian North West Shelf during the survey undertaken by AGSO along 5 profiles of total length 2764 km. Data in these experiment were recorded to maximum offsets of 300 km.

Between 1990 and 1994, AGSO - Geoscience Australia acquired approximately 35,000km of regional, mostly deep (commonly 15s record length), 2D seismic reflection data along the northern and north-western continental margins of Australia. These data were shot primarily to provide a structural and tectonic framework to assist petroleum exploration companies in their search for hydrocarbons in the region, as well as an aid to understanding the margin's geological evolution. This CD contains line drawings of interpretations of all of the lines that compose the Geoscience Australia's regional grid. The interpretations (horizons and faults) were made by an external contractor to Geoscience Australia, IKODA Pty Ltd, using Landmark software, and build on previously published Geoscience Australia work of parts of the grid (e.g. papers in Purcell & Purcell, 1994) as well as tying to Geoscience Australia-sponsored detailed NW Shelf and Timor Sea high-resolution seismic studies.

The 2008 Rankins Springs Seismic Survey was a joint initiative by Geoscience Australia and NSW Department of Primary Industries under the Onshore Energy Security Program (OESP) in the under-explored southeastern Darling Basin. Regional acquisition parameters of 300 channels, 40 m group interval and 80 m vibration point interval nevertheless allowed detailed imaging of a 3 second (TWT) thick sedimentary sequence in the Yathong Trough. Use of three 12 second vari-sweeps from truck mounted Hemi 50 (50,000 lb) vibrators provided sufficient energy to image from immediately below regolith to the Moho. The sweep frequency ranges 6 - 64, 10 - 96 and 8 - 80 Hz were chosen both for deep penetration and high resolution in the sedimentary section. In-field processing produced a high quality preliminary section on a daily basis using an iterative process of automatic residual statics calculation on a deep gate and interactive stacking velocity analysis. Both automatic statics and stacking velocity were essential for successful imaging, but velocity was more important, as initial estimates based on first arrival velocities produced a degraded section. The field seismic section clearly shows a fault bounded trough, with evidence of compressional structures in the upper part and hints of underlying older sedimentary basins. The in-field stacking velocity analysis also provided immediate evaluation of the maximum depth of the trough, namely 6 km, deeper than expected. Efficient in-field processing allows early notification to project partners of a successful survey, facilitating future planning, and provides a sound basis for streamlined subsequent processing.

The Capel and Faust basins are located in a remote part of deepwater offshore eastern Australia. They are largely Cretaceous rifts formed within a 1600 km long ribbon of continental crust (the Lord Howe Rise) that became detached from Australia during the fragmentation of the eastern Gondwana plate margin and the opening of the Tasman Basin. As part of Geoscience Australia (GA)'s ongoing work to identify and evaluate the resource potential of Australia's offshore frontier basins, approximately 6 000 km of industry-standard, 106-fold 2D seismic data was acquired over the Capel and Faust basins during late 2006 and early 2007. These data supplemented earlier, sparse regional seismic data and were complemented by the acquisition of approximately 24 000 km2 of multibeam bathymetry and 11 000 line kilometres of shipboard gravity and magnetic data by GA in late 2007. This record details the interpretation of the seismic data and is intended to complement the release of a digital version of the interpretations in workstation formats (GeoFrame, Kingdom). Scientific conclusions drawn from the seismic interpretations and, very importantly, from an integration of the seismic, potential field and other data sets are beyond the scope of this record and are published in other GA Records, scientific papers and conference proceedings volumes.

In 2008-09, under the Offshore Energy Security Program, Geoscience Australia (GA) acquired 800 km of 2D seismic (Southwest Margin seismic survey) along with regional gravity and magnetic data (Southwest Margin Marine Reconnaissance survey) in the southern Carnarvon Basin. Data acquisition targeted the western Bernier Platform, as well as the adjoining poorly explored deepwater (>500m) parts of the margin, where prominent gravity lows indicated likely southern extension of the Exmouth Sub-basin and northern extension of the Houtman Sub-basin. The 2011 Acreage Release areas in the frontier part of the southern Carnarvon Basin are about the same size as the combined Rankin Platform, Barrow and Dampier Sub-basins. Only two wells (Pendock 1A and Herdsman 1) have been drilled in and in close proximity to these Acreage Release areas, providing only limited information on stratigraphy and petroleum systems of the region. The newly acquired seismic and potential field data were used to evaluate structure, stratigraphy and petroleum potential of the area. Analysis of the seismic data resulted in better understanding of tectonic and depositional history, including the role of extensive Early Cretaceous volcanism. Sufficient sediment thickness and a wide-range of possible structural and stratigraphic plays have been identified in the 2011 Acreage Release areas.

Steeply dipping reflectors have been recognised on stack data for the Lachlan Fold Belt (up to 60º) and the Tanami Province (up to 70º), demonstrating that significant dip filtering does not occur during acquisition with regional parameters. DMO correction is essential during processing to correctly image such features. These events appear to be real reflections not reflected refractions or diffractions, as proved by analysis of amplitude, frequency and moveout on shot records. In the Tanami case, the reflection is related to a small circular feature in the potential field image, possibly the expression of a granite stock. Migration proved problematical, as most migration algorithms could not simultaneously migrate the steep dips and remain artefact free in other parts of the section, suggesting that interpretation must be done on multiple sections in such cases.

The 2005 Tanami Seismic Survey consisted of 720 km of deep crustal seismic reflection data acquired along 4 lines. The processing was aimed at obtaining a high quality image of the crust from the Moho to the surface, with particular emphasis on imaging shallow features and steeply dipping reflectors. The key processing steps applied here included refraction and automatic statics, spectral equalisation, detailed velocity analysis pre and post DMO, and omega-x migration. Near surface features were better imaged using a floating datum technique for refraction statics application, with only the residual CDP static applied before NMO correction, and the mean CDP static after migration. Offset regularization of CDP gathers pre DMO employed trace interpolation based on dip coherency which had the dual advantage of improving signal to noise, and normalizing amplitudes in low-fold areas, thus reducing migration smiles.

Presented at the Evolution and metallogenesis of the North Australian Craton Conference, 20-22 June 2006, Alice Springs. Deep seismic reflection profiling has been used for many years to provide images of the continental crust in the third dimension (depth) across parts of Australia. Prior to the 2005 Tanami deep seismic survey, a limited amount of deep seismic reflection profiling was conducted in central and northern Australia. A major survey in 1985 examined the geometry of the Amadeus Basin and Arunta Block (Goleby et al., 1988). Subsequent surveys examined the Officer Basin and southern Musgrave Province in 1993 (Korsch et al., 1998) and the southern McArthur Basin in 2002 (Rawlings et al., 2004). Here, we review aspects of these surveys and briefly examine the implications for the tectonics of the region. <p>Related product:<a href="https://www.ga.gov.au/products/servlet/controller?event=GEOCAT_DETAILS&amp;catno=64764">Evolution and metallogenesis of the North Australian Craton Conference Abstracts</p>