From 1 - 10 / 498
  • Magnetotelluric data were acquired for Geoscience Australia by contract along the north-south 08GA-C1-Curnamona seismic traverse to the east of Lake Frome from November 2008 to January 2009 as part of the Australian Government's energy security initiative. 25 sites were spaced an average of 10 km apart, and five-component broadband data were recorded with a frequency bandwidth of 0.001 Hz to 250 Hz and dipole lengths of 100 m. Apparent resistivity and phase plots are presented, along with dimensional analyses of the data based on rotational invariants, the representation of the data by the phase tensor, and Parkinson arrows. These analyses provide insight into the complexity of the Earth conductivity giving rise to the MT responses and are a useful precursor to modelling.

  • The Petrel Sub-basin Marine Survey was undertaken in May 2012 by Geoscience Australia and the Australian Institute of Marine Science to support assessment of CO2 storage potential in the Bonaparte Basin. The aim of sub bottom profiling was high resolution data to investigate regional seal breaches and potential fluid pathways. The sub bottom profiler data were acquired aboard the AIMS RV Solander, a total of 51 lines and 654 line km. Acquisition employed a Squid 2000 sparker and a 24 channel GeoEel streamer. Group interval of 3.125 m and shot interval of 6.25 m resulted in 6 fold stacked data. Record length was 500 ms, sampled every 0.25 ms. Rough sea conditions during the trade winds resulted in obvious relative motion between source and streamer. Multichannel seismic reflection processing compensated for most of the limitations of sparker acquisition. Front end mute and band pass filter removed low frequency noise. Non surface consistent trim statics corrected for the relative motion of sparker and streamer, aligning reflections pre stack and improving signal to noise. Post stack minimum entropy deconvolution both suppressed ghosting and enhanced high frequencies (>1000 Hz). Vertical resolution of better than 1 m allowed delineation of multiple episodes of channelling in the top 100 m of sediment. Imaging of small channels was improved by collapsing diffractions with finite difference migration.

  • Magnetic field interpretation is not an alternative to palaeomagnetic methods of recovering remanent magnetization information, both because it deals with the resultant of induced and remanent magnetizations and because confidence in recovered magnetization directions cannot match than provided by direct palaeomagnetic measurement. Nevertheless, magnetic field interpretation is highly complementary to palaeomagnetic studies. Palaeomagnetism provides detailed information from small, localised samples whereas magnetic field interpretation provides estimates of the bulk magnetization of substantial volumes (which may be completely buried and un-sampled by boreholes). Without palaeomagnetic and rock magnetic studies much of the geological information latent in magnetic field measurements cannot be accessed, and without the coverage of magnetic field data the extents and relationships of subsurface magnetization events revealed by palaeomagnetic studies cannot be fully mapped.

  • Now in its third year, Geoscience Australia's Onshore Energy Security Program has acquired several suites of regional geological and geophysical data. The data include several deep seismic reflection surveys that have been designed to image: - basement provinces with high geothermal gradients that may contain Uranium enrichments and are potential candidates for geothermal energy, - geological terrane boundaries and - sedimentary basins that are known to host petroleum system elements but are under-explored. Seismic signals are recorded down to 20 seconds two-way-time (TWT) which corresponds to 25-35 km depth depending on dominant lithologies. Basinal sections normally extend down to 6-8 secTWT and the data is of such high quality that any section of the seismic profile can be enlarged without significant loss of resolution. Deep reflection surveys are able to image the relationship between crystalline basement and overlying basin sequences very clearly and also allow interpretations of structural styles as well as impacts of deformational processes on the basin-fill. A new basinal section was discovered beneath the Eromanga Basin suite of sediments. Named the 'Mullangera Basin', its structural style and basement relationship seem to indicate some affinity with the Georgina Basin further west. The succession is clearly composed of several sequences that contain both fine-and coarse-grained sediments. If a geological relationship with the Georgina Basin can be ascertained, a new hydrocarbon prospective area could be delineated. Another new section was discovered beneath the Devonian section of the Darling Basin. Judging by the fast acoustic velocities the entire basin-fill sequence appears to be very dense and therefore largely non-porous and of low permeability.

  • An orogenic cycle typically follows a sequence of events or stages. These are basin formation and magmatism during extension, inversion and crustal thickening during contractional orogenesis, and finally extensional collapse of the orogen. The Archaean granite-greenstone terranes of the Eastern Yilgarn Craton (EYC) record a major deviation in this sequence of events. Within the overall contractional stage, the EYC underwent a lithospheric-scale extensional event between 2665 Ma and 2655 Ma, resulting in changes to the entire orogenic system. These changes associated with regional extension include: the crustal architecture; greenstone stratigraphy; granite magmatism; thermo-barometry (PTt paths); and structure. Synchronous with these changes was the deposition of the first significant gold, and it is likely that the intra-orogenic extensional event was one of the critical factors in the region's world-class gold endowment.

  • Summary of GA's plans for marine seismic and reconnaissance surveys off southwestern Australia in 2008/09 as part of the Offshore Energy Security Program

  • In the 2011/12 Budget, the Australian Government announced funding of a four year National CO2 Infrastructure Plan (NCIP) to accelerate the identification and development of suitable long term CO2 storage sites, within reasonable distances of major energy and industrial emission sources. The NCIP funding follows on from funding announced earlier in 2011 from the Carbon Storage Taskforce through the National Carbon Mapping and Infrastructure Plan and previous funding recommended by the former National Low Emissions Coal Council. Four offshore sedimentary basins and several onshore basins have been identified for study and pre-competitive data acquisition.

  • A study of the consistency of gust wind speed records from two types of recording instruments has been undertaken. The study examined the Bureau of Meteorology's (BoM) wind speed records in order to establish the existence of bias between coincident records obtained by the old pressure-tube Dines anemometers and the records obtained by the new cup anemometers. This study was an important step towards assessing the quality and consistency of gust wind speed records that form the basis of the Australian Standards/NZ Standards for design of buildings for wind actions (AS/NZS 1170.2:2011 and AS 4055:2006). The Building Code of Australia (BCA) requires that buildings in Australia meet the specifications described in the two standards. BoM has been recording peak gust wind speed observations in the Australian region for over 70 years. The Australia/New Zealand Wind Actions Standard as well as the wind engineering community in general rely on these peak gust wind speed observations to determine wind loads on buildings and infrastructure. In the mid-1980s BoM commenced a program to replace the aging Dines anemometers with Synchrotac and Almos cup anemometers. During the anemometer replacement procedure, many localities had both types of anemometers recording extreme events. This allowed us to compare severe wind recordings of both instruments to assess the consistency of the recordings. The results show that the Dines anemometer measures higher gust wind speeds than the 3-cup anemometer when the same wind gust is considered. The bias varies with the wind speed and ranges from 5 to 17%. This poster presents the methodology and main outcomes from the assessment of coincident measurements of gust wind speed.

  • Geoscience Australia has developed an interactive 3D viewer for three national datasets; the new Radiometric Map of Australia (Geoscience Australia 2009b), the Magnetic Anomaly Map of Australia (Geoscience Australia 2004), and the Gravity Anomaly Map of the Australian Region (Geoscience Australia 2008). The interactive virtual globe is based on NASA's open source World Wind Java Software Development Kit (SDK) and provides users with easy and rich access to these three national datasets. Users can view eight different representations of the radiometric map and compare these with the magnetic and gravity anomaly maps and satellite imagery; all draped over a digital elevation model. The full dataset for the three map sets is approximately 55GB (in ER Mapper format), while the compressed full resolution images used in the virtual globe total only 1.6GB and only the data for the geographic region being viewed is downloaded to users computers. This paper addresses the processes for selecting the World Wind application over other solutions, how the data was prepared for online delivery, the development of the 3D Viewer using the Java SDK, issues involving connecting to.