At the request of the Australian Atomic Energy Commission, the Bureau of Mineral Resources, Geology & Geophysics conducted a seismic refraction survey on the site chosen for construction of a nuclear power station. The purpose of the survey was to determine the foundation conditions at the site and the properties of the rocks in relation to excavation methods and support of the proposed structures. The bedrock of the area consists of Permian sandstone (Jervis Bay Sandstone) overlain in places by unconsolidated Quaternary beach and dune sands. During the seismic work it was found that the sandstone beds have a relatively wide range of seismic velocities; often a higher-velocity bed overlies a lower-velocity bed, and this makes seismic refraction work difficult and less accurate. This is confirmed by laboratory measurements of seismic velocities on drill cores. Thin beds of higher- and lower-velocity sandstones occur, some too thin to be resolved by the seismic method. The seismic profiles presented must be considered bearing in mind these difficulties, Haterial sufficiently consolidated for foundations is shallow, and the seismic velocities indicate that some blasting will be necessary to excavate to the desired depth of 10 feet above mean high water level.

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.

The Undilla Basin, in north-western Queensland, is a small sedimentary basin containing Cambrian limestones which adjoin the widespread but undated CamoowJal Dolomite to the West. In the latter part of 1961 the Bureau of Mineral Resources, Geology and Geophysics did a brief reconnaissance seismic survey lasting about seven weeks in the Undilla Basin. This Record describes briefly the work done and results obtained. The occurrence of limestone near the surface throughout the basin presented difficult problems in the application of the reflection and refraction seismic methods but some progress was made towards the solution of these problems.

The Oaklands-Coorabin Coalfield in the Riverina Division of New South Wales has been known for many years. Seismic refraction tests were carried out on a number of sections to assist in the interpretation of the gravity results during July and Sepetember, 1949.

A reconnaissance seismic reflection and refraction survey in the East Otway Basin, Victoria, was carried out by the Bereau of Mineral Resources from mid-February to mid-June 1967. The objective of the survey was to determine whether the gravity low areas of the Torquay Embayment and Port Phillip Sub-Basin in the eastern part of the Otway Basin contain thick Cretaceous sediments like those which has shown potential hydrocarbon source and reservoir characteristics in the western part of the Otway Basin. Nine reflection and five refraction traverses were recorded in the gravity low areas of the Barwon Trough and Port Phillip Sub-basin. Single-coverage reflection results of variable quality were obtained. Evidence for the presence of Tertiary section is provided by shallow reflections of good to fair quality, but the evidence for Cretaceous sediments is tenuous because of the poor quality of the deeper reflections, some of which may be multiples. The presence of several faults, onlappings and pinch-outs is also indicated. The refraction results are considered unreliable because of the difficulty of interpreting the discontinuous profiles and because of the mapped and suspected faults and pinch-outs in the sections.

A seismic survey extending over the Poole Range and Price's Creek areas and the Pinnacle Fault, near the north-eastern boundary of the Fitzroy Basin was corducted during the winter of 1953. The Poole Range Dome has been mapped in outcropping rocks of Permian age, but its western closure is not certain. It is at the south-eastern end of a line of anticlinal folding which includes the St. George Range Dome and Nerrima Dome. The target beds for an oil test bore would be the Devonian and/or Ordovician rocks, which crop out on the north-eastern side of the Pinracle Fault, and over which the Permian rocks of the Poole Range are believed to lie unconformably. The seismic results indicate a thick section of sediments on the south-western side of the Pinnacle Fault and show a fair degree of conformity between shallow and deep reflections on the northern flank of the dome. Further investigatioll was made in 1954 around the flanks of the dome to determine whether or not the domal structure persists at depth, but the interpretation of the results of the 1954 survey is not yet complete. The Ordovician rocks on tbe north-eastern side of the Pinnacle fault are shown to have a probable unexposed thickness of about 900 feet.

An experimental seismograph survey was carried out near Heywood in the Western District Basin, south-western Victoria, during November and December, 1956 by the Bureau of Mineral Resources, Geology and Geophysics. The work was requested by Frome-Broken Hill Pty. Ltd. and was intended primarily to ascertain if reflections from deoper sediments could be recorded through a surface layer of basalt which covers considerable areas in the Western District of Victoria. Several short traverses were shot during the survey at places where a variety of surface conditions for seismic exploration could be tested. Pattern and air-shooting techniques were tried as well as the conventional single shot-hole technique. Good reflections were recorded from depths down to eleven thousand feet in areas where there was no basalt. Some apparent reflections of poor quality were recorded at times as great as 5 seconds after the shot was fired. An attempt has been made to correlate the reflections with stratigraphic horizons. Reflections were obtained from strata beneath a basalt cover in some places when explosive charges were fired in single shot holes; reflection quality was improved when pattern and air-shooting techniques were used.It was not possible to record reflections through a cover of tuff containing basalt bands on the slopes of Mt. Clay. Pattern and air-shooting were tried unsuccessfully. Sub-surface information in the Heywood area is obtainable by seismic exploration and techniques for gaining the best information from the seismic method are discussed.

A reconnaissance seismic survey was made in the area of Quilpie and Et.omanga in south-western Queensland. Traverses crossed the Harkaway, Pinkilla, and Tallyabra Domes. Reflection horizons were correlated with horizons within the Mesozoic sediments, and one persistent reflection was correlated with a horizon near the top of the Palaeozoic sediments. A thickness of sediments of up to 15,000 ft, including up to 11,000 ft of Palaeozoic rocks, was indicated on the flanks of the Harkaway and Pinkilla Domes. Results were compared with existing gravity data. Suggestions of faulting are based on seismic and gravity evidence taken together and also on gravity evidence alone in locations not covered by the seismic work.

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.

Between April and July 1962, a seismic party from the Bureau of Mineral Resources, Geology and Geophysics made a seismic reflection and refraction survey in the Moree area of New South Wales. The main purpose of the survey was to investigate whether the southern extension of the Bowen Basin beneath the Great Artesian Basin from Meandarra to Toobeah continued as far south as Moree and joined the Sydney Basin. Three east-west traverses were shot using a method of reconnaissance reflection shooting, the first near Dolgelly Bore, the second through Moree, and the third through Bellata. The third traverse was extended eastward as far as the Horton River to investigate the Hunter-Bowen Thrust zone. In addition, three north-south refraction traverses were shot in the middle, and on both ends, of the east-west traverse through Moree. A north-south reflection traverse was shot north of Dolgelly Bore.Results in the Moree and Bellata areas were of poor quality and in the Bellata area in particular, owing to surface basalt flows, little information was obtained. The Hunter-Bowen Thrust area was not distinguished by the seismic work. The seismic results indicated that the trough of sediments extending southwards through Dolgelly Bore was at least 7500 ft deep south of Dolgelly Bore. The eastern margin of the trough is probably an overthrust fault. In the Moree area, two troughs were indicated, viz. the Biniguy Trough in the east where about 7000 ft of sediments was estimated separated by the Pallamallawa Ridge from the Moree Trough in the west where about 11,000 ft of sediments was estimated. Poor results in the Bellata area failed to indicate whether the Moree Trough joined the Sydney Basin.