Following a month of preliminary experimental seismic work in the latter part.of 1964 the Bureau of Mineral Resources carried out a reconnaissance seismic survey of the southern part of the Georgina Basin, mainly in the Northern Territory, from April to October 1965. In most areas reflections proved very difficult to obtain. A number of different techniques were tried, including various shot andgeophone pattern arrangements, noise testing,collinear offset shooting, airshooting and multiple coverage, but no technique was found which was generally successful in providing useful reflections. The seismic results tended to confirm gravity indications that there is a shelf area between BMR 12 Bore and Tobermory and provided no indications that there are deep Palaeozoic troughs similar to the Toko -Syncline in the survey area.

A seismic velocity survey was carried out in Associated Freney Oilfields Nerrima No. 1 Bore by the Bureau of Mineral Resources on the 10th August 1955. The well is situated on the Nerrima Dome in the Fitzroy Basin, W.A. Some trouble was experienced with cable breaks for the shallow part of the hole, but in general it was possible to recognise the true formation break. Average measured velocities ranged from 8000 ft/sec near the top to 12,200 ft/sec for the total depth of the bore.

In 2008, as part of the Australian Government's Onshore Energy Security Program, Geoscience Australia, acquired deep seismic reflection, wide-angle refraction, magnetotelluric (MT) and gravity data along a 250 km east-west transect that crosses several tectonic domain boundaries in the Gawler Craton and also the western boundary of the South Australian Heat Flow Anomaly (SAHFA). Geophysical datasets provide information on the crustal architecture and evolution of this part of the Archean-Proterozoic Gawler Craton. The wide-angle refraction and MT surveys were designed to supplement deep seismic reflection data, with velocity information for the upper crust, and electrical conductivity distribution from surface to the upper mantle. The seismic image of the crust from reflection data shows variable reflectivity along the line. The upper 2 s of data imaged nonreflective crust; the middle to lower part of the crust is more reflective, with strong, east-dipping reflections in the central part of the section.The 2D velocity model derived from wide-angle data shows velocity variations in the upper crust and can be constrained down to a depth of 12 km. The model consists of three layers overlying basement. The mid-crustal basement interpreted from the reflection data, at 6 km in depth in the western part of the transect and shallowing to 1 km depth in the east, is consistent with the velocity model derived from wide-angle and gravity data. MT modelling shows a relatively resistive deep crust across most of the transect, with more conductive crust at the western end, and near the centre. The enhanced conductivity in the central part of the profile is associated with a zone of high reflectivity in the seismic image. Joined interpretation of seismic data supplemented by MT, gravity and geological data improve geological understanding of this region.

Following a gravity survey of the Perth Basin in 1951-52 (Thyer and Everingham, 1956), in which it was indicated that a sedimentary thickness of about 35,000 ft was probably present in the Perth Basin, several seismic traverses were surveyed across the Basin. This Record deals with one such reflection traverse which was surveyed between Quindalup and Donnybrook. The purposes of the survey were to find the thickness and dip of the sediments and to discover any faulting or folding within them. Results of the survey were inconclusive regarding the depth to basement but indications are that it is at least 8000 ft in the deepest part of the B,sin along this traverse. The sediments appear to be folded and faulted. There is evidence for the existence of a major fault east of the Dunsborough Fault, and the existence of the Whicher Fault was tentatively confirmed.

A seismic reconnaissance, traverse was surveyed for 20 miles along an east-west line,. 10 miles 'north of -Carnarvon, as part of a regional investigation of the southern part of the Carnarvon Basin, W.A. Both reflection and refraction techniques were used, and the results were Correlated, where possible, with the known formations in the Pelican Hill bore. Several reflecting horizons could be followed although reflections from below the level of the Cretaceous/Palaeozoic unconformity were badly interfered by multiples. The refraction method was successful, and recorded three main refractors with velocities of 14750.ft/sec, 18400 ft/sec, and 20,280 ft/sec. The main feature of the section obtained is a broad antiform within the Palaeozoic sediments, shown particularly by the 20 2 280 ft/sec refractor, which is_a good marker. for structural mapping. This marker has been tentatively correlated with the Dirk Hartog Dolomite, which would suggest that the strata underlying the Gneudna Formation in the Pelican Hill bore belong to the Nanyarra Greywacke rather than the Tumblagooda Sandstone. Overall the profile of the 20 2 280 ft/sec marker has a slight west dip from about 4000 feet at the eastern end to about 5000 feet at the western end of the traverse. The Cretaceous/Palaeozoic unconformity was fairly flat at a depth of about 1500 feet. Indications from the reflection cross-section and from the profile of the 18,400.ft/sec refractor are that the sediments between the two above horizons are similar in structural attitude to the deeper horizon.

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.

Despite long history of studies the Wallaby Plateau offshore Western Australia remains a controversial feature. Analysis of interval seismic velocities from Geoscience Australia's 2008/09 seismic survey 310 in conjunction with seismic reflection interpretation provides new insights into the geology of the Plateau. Seismically distinctive divergent dipping reflector sequences (DDRS) have been identified. The seismic character of the DDRS is similar to seaward dipping reflector sequences (SDRS) of inferred volcanic composition. Initial analysis of seismic velocity profiles indicated affinities between the DDRS packages and known sedimentary strata in the Houtman Sub-basin. Effect of water loading on seismic velocities is commonly ignored in offshore studies. However, direct comparative analysis of interval velocity patterns between areas of significantly different water depth requires various water pressure related changes in velocity to be accounted for. There are controversies in methodology and application of water depth adjustment to seismic velocities, and presentation of velocity models as function of pressure rather than two-way time, or depth emerges as a possible solution. Water depth adjustment of seismic velocities analysed in our study reduces distinction between SDRS, DDRS and sedimentary strata such that discrimination between volcanic and sedimentary strata in DDRS or SDRS is equivocal. A major uncertainty of this interpretation is due to a lack of the reference velocity model of SDRS and DDRS investigated globally.

The Bureau of Mineral Resources'No. 2 seismic party conducted a Survey over the Palm Valley Anticline 80 miles west of Alice Springs, from 2nd November to 22nd November 1961. The seismic reflection method showed (a) the anticlinal structure existed at depth and (b) at the northern end of the main north-south traverse in the Missionary Plains north-dipping reflections were recorded from about 2500-ft depth. A shallow refractor was recorded in which the velocity Was 17,800 ft/sec. This refractor, which could not be positively identified, prevented, any useful deeper refraction information being recorded.

An experimental seismic survey using both refraction and reflection techniques was carried out in April, 1958, near Morwell in the Latrobe Valley at the request of the State Electricity Commission of Victoria. The object of the survey was to find if the method was of value in mapping the structure of the coal measures of the Latrobe Valley and in providing information on the depth to and type of basement underlying the coal measures. Work was concentrated in an area south-west of Morwell on the southern limb of the Latrobe Syncline. The results obtained indicate that the seismic method may be applied successfully to geological problems of the Latrobe Valley and may provide useful control data for the interpretation of surface geological and gravity mapping. Various interpretations of the results are discussed and although some ambiguity exists, it might be overcome when more work is done, particularly if an accurate knowledge of the velocities of the coal easures is obtained. It has been possible by means of refraction work to map the extension of the basalt which crops out on the southern margin of the Latrobe Syncline beneath the coal measures with reasonable certainty.

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