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  • Between October 2008 and February 2009, Geoscience Australia undertook two major surveys off the coast of Western Australia. Areas of interest included the Mentelle and northern Perth Basins, the Southern Carnarvon Basin, the sourthern Exmouth Sub-basin (Northern arnarvon Basin) and the Wallaby Plateau. These surveys collected a range of data, including 7300 kilometers of industry-standard seismic reflection data and 43000 line kilometers of gravity and magnetic data. In addition to the new data collected, Geoscience Australia has reprocessed 11700 line kilometres of open file 2D seismic data that exists within the survey area. This data is available for purchase as part of the Southwest Margin Data Package.

  • Prior to the development of Australian-specific magnitude formulae, the 1935 magnitude corrections by Charles Richter – originally developed for southern California – was almost exclusively used to calculate earthquake magnitudes throughout Australia prior to the 1990s. Due to the difference in ground-motion attenuation between southern California and much of Australia, many historical earthquake magnitudes are likely to be overestimated in the Australian earthquake catalogue. A method has been developed that corrects local magnitudes using the difference between the original (inappropriate) magnitude corrections and the Australian-specific corrections at a distance determined by the nearest recording station likely to have recorded the earthquake. These corrections have reduced the rates of local magnitudes of 4.5 in the historical catalogue by about 30% since 1900, while the number of magnitude 5.0 earthquakes has reduced by about 60% in the same time period. The reduction in the number of moderate-to-large-magnitude earthquakes over the instrumental period yields long-term earthquake rates that are more consistent with present-day rates, since the development of Australian-specific magnitude formulae. The adjustment of historical earthquake magnitudes is important for seismic hazard assessments, which assume a Poisson distribution of earthquakes in space and time.

  • Initial 2D seismic survey using mini-vibroseis with high frequency band 10 - 150Hz. This seismic survey is part of the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) projects.

  • Geoscience Australia in collaboration with the Geological Survey of Western Australia conducted a seismic testing program on the Eucla Basin carbonate sediments during May 2012, during a survey to collect deep seismic data across the western Eucla Basin. These data were collected as part of the Albany-Fraser Seismic Survey that consists of three traverses in south-east Western Australia with a total length of 671 km. The major aim of this survey was to image the basement relationship between the Yilgarn craton, the Albany-Fraser zone, and basement rocks further east. Much of this eastern area is covered by the limestones of the Eucla Basin, and there has been little seismic data acquired in this area. These tests were required to confirm the feasibility of collecting deep seismic data beneath the limestones through the region. Geoscience Australia has had little success in penetrating the limestones of the Eucla Basin in previous surveys. Several sets of recording parameters were tested, including 10 Hz geophones and lower frequency 4.5 Hz geophones as parallel spreads. Also, linear upsweeps were compared to low-dwell non-linear upsweeps designed to introduce more low frequency energy into the signal. Initial results from the testing program were encouraging. Production data were subsequently collected along the Trans Australia Railway access road as far as Haig, using Geoscience Australia's standard deep crustal seismic acquisition parameters.

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  • An experimental seismic survey was conducted at Surat, Queensland, on behalf of the Australisa Oil and Gas Corporation Limited during a five week period from May 28th to July 2nd. 1958. The area lies within the southeastern portion of the Great Artesian. Basin on Authority to Prospect No. 36P and, sel the evidence of numerous bores near Roma, and a few other scattered bore logs, is considered to contain sediments suitable for the generation and accumulation of hydrocarbons in possible, economic vantities. A local geological survey by the Australian Oil & Gas Corporation suggested a structure of considerable dimensions - the 'Weribone Uplift' - which, if substantiated, would provide a promising location for a stratigraphic test bore. The experimental survey conducted by the Bureaushowed that useful results could be obtained throughout the area by conventional methods of reflection and refraction shooting. The reflection shooting indicated a fairly uniform sedimentary section with generally flat-lying beds and a probable total thickness of 7,000 to 8,000 feet. The refraction work recorded several velocities: including one near 19,000 f/s which is assumed to be a basement velocity. Depths measured to this high Velocity refractor support the estimate of the thickness of sediments made from the reflection cross-section and indicate 4 south component of dip of about 40 ft. per mile across the area surveyed. Neither the reflection nor the refraction work gave any evidence for the existence of the 'Weribone Uplift'. However, the more northerly refraction traverse indicated a local component of north dip at basement depth, and a single reflection record shot along that traverse suggested a substantial thickening of the deeper sediments towards the north. Insufficient seismic work was done to estimate the northwards extent of this dip. Such limited evidence might well indicate a purely local irregularity in basement topography. On the other hand, the north dip could be extensive, and therefore structurally significant. Any further seismic work contemplated in this area should be directed, in the first instance, towards checking this possibility.

  • A seismic velocity survey of the APM Development Pty Limited No. 1 bore at Rosedale, Victoria, was made by the Geophysical Branch of the Bureau on the 3rd May 1960 using a TIC three-component well geophone. Measurements were taken with the geophone suspended in the well at selected intervals down to 5500 ft. It was apparent that signals reached the geophone by transmission along the cable by which it was suspended, and these interfered with the signals reaching the geophone along a path directly through the ground. This made interpretation difficult; however, by careful inspection of both the vertical and horizontal components of the signals received by the geophone at each depth, an interpretation has been made that yields a series of velocity/depth determinations. The average vertical velocity increases from 5000 ft/sec at the surface to 8930 ft/sec at a depth of 5500 ft. The average velocity in the Tertiary (0-2159 ft below datum) was computed to be 6420 ft/sec; the -werage velocity in the Mesozoic rocks penetrated (2159-5314 ft below datum) was 12,180 ft/sec. Two reflection spreads laid out and recorded in the vicinity of the bore showed the presence of reflectors at depths estimated to be in excess of 7700ft.

  • Towa.:ccis the end of 1960 , the Bureau. of Mineral Resources, Geology and Geophysics made a brief seismic survey in the Winton area of Queensland to resolve an apparent contradiction between the interpretations of gravity and aeromagnetic results previously obtained in the area. Gravity and aeromagnetic results both suggested the occurrence of a large fault or fault zone about 20 miles north-west of Winton, but the gravity and aeromagnetic interpretations differed regarding the direction of throw of the fault. A nine-mile seismic reflection traverse was surveyed across the supposed fault. The seismic results indicate the presence of a large fault or monoclinal fold with dowthrown side nouth-wast as suggested by the gravity values and also a smaller fault or monocline about two miles south-east with downthrown side south-east. The variations in thckness of Mesozoic rocks caused by these features were insufficient to explain the observed Bouguer gravity anomaly values, but the seismic results left open the possibilitues that there may be a considerable thickness of pre-Mesozoic sedimemts north-west of the main monocline or fault. It is postulated that the steep gravity gradient observed may be due to a large fault whose main movement took place in pre-Mesozoic times. Indications are that there is 5000 to 6000 ft of Mesozoic sediments in tha area.