seismic refraction
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Between August and December 1960 a seismic party from the Bureau of Mineral Resources carried out a reconnaissance seismic survey, using reflection and refraction techniques, across the Murray Basin. Traverses were placed at selected localities at Carrathool, Hay, Maude, Balranald, Wentworth, Merbein, Lake Victoria, and Loxton. In general, the results show that the Basin, at least along the line of traverse, consists of essentially undisturbed sediments above a high-velocity basement. The thickness of Basin sediments ranges from about 900 ft at Carrathool to 2200 ft at Lake Victoria and Merbein. Most of the sediments are of Tertiary age, with Mesozoic at Loxton and Wentworth and perhaps at other traverses in the western part of the Basin. The seismic velocity in the sediments has a typical value of about 6000 to 7000 ft/sec, while the velocity in the basement ranges from 15,750 ft/sec (at Hay) up to 20,000 ft/sec (at Lake Victoria). The geological nature of basement is not known, but it is considered that it definitely marks the floor of the Tertiary (or Tertiary - Mesozoic) basin. Refraction velocities alone are of doubtful value in identifying the floor, as it is known that crystalline basement, metamorphosed sediments, or unmetamorphosed sediments such as limestone, may have velocities within this range.
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Presentation delivered at the Tasman Frontier Workshop, 89- March 2012
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Aeromagnetic and gravity surveys were made in the Tambo-Augathella area by Magellan Petroleum Corporation in 1959 and 1960 respectively. A probable fault shown in the magnetic interpretation is almost coincident with a zone of steep gravity gradients which was interpreted as indicative of a fault or of steeply dipping strata. However, the normal gravity interpretation would indicate a deeper cross-section to the south-east of this zone, whereas the magnetic interpretation suggests that the fault is downthrown to the northwest. The present survey was undertaken by the Bureau of Mineral Resources to find out which interpretation was the more probable. A reflection seismic traverse was shot at right angles to the closed gravity 'high' and across the zone of steep gravity gradients. Results show that the closed gravity 'high' is the expression of an anticline and that the zone of stoep gravity gradients is caused by steep dip to the south-east on the flank of the anticline. The gravity interpretation is therefore found to be more representative of actual conditions.
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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.
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Seismic refraction investigations were made at five sites in the vicinity of Alice Springs, Northern Territory, by the Bureau of Mineral Resources in August 1962. This work was done, at the request of the Bureau of Mineral Resources Observatory Group, to select the most suitable site for a seismological observatory. In view of the desirable features for such a site - a bedrock having a high seismic velocity and a bedrock at shallow depth - a site about three miles west of Alice Springs is recommended as the most suitable; the bedrock material has a velocity of 17,800 ft/s and the thickness of overburden is less than 20 ft.
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A four and a half month seismic survey has been carried out in the Poole Range area of the Fitzroy Basin by C. G. G. where both the reflection and refraction methods have been tested. Reflection experiments lead to a high multiplication of geophones and shot-holes patterns. However, tests were too limited and too scattered to allow for definite conclusions regarding the best recording procedure. The refraction method has been used to provide information regarding the extension at depth of Poole Range surface anticline. The same method was used for a reconnaissance survey on the regional gravity anomaly 16 A. Besides shallow markers, two and sometimes three deep markers were followed simultaneously. The results obtained during the survey indicate that: Poole Range surface structure has no extension at depth; - Two high zones, separated by a narrow trough appear to correspond to the gravity anomaly 16 A. The eastern high zone is a wide dome with a closure of about 4,000 ft at the level of the deeper marker. The western high zone corresponds to a shelf-like area of the deeper marker. It is overlain by sedimentary formations where facies changes are suggested by rapid variations of the marker's velocities. This is the shallowest area of the survey with a 15,000 ft/ sec marker at a depth of less than 10,000 ft. Delimination of the most interesting structural locations would require the carrying out of supplementary traverses. A tentative interpretation makes the deeper marker a probable Proterozoic level with depths ranging from 15,000 feet to 30,000 feet. The two others might represent Devonian and Ordovician formations.
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Several seismic surveys were made by the Bureau of Mineral Resources, Delhi Australian Petroleum Ltd, -Phillips Petroleum Company, and L. H. Smart Oil Exploration Company Ltd during the period from 1959 to 1963 between Eula and the Queensland/South Australia border area of the Eromanga Basin. This report covers the seismic work done by the Bureau of Mineral Resources in 1962 and 1963 and also incorporates the results of the work done by the private oil exploration companies. It aims at providing information on the nature and structure of the rocks underlying the Mesozoic sediments of the Eromanga Basin. The seismic results have been interpreted with reference to the geology as known from the Delhi-Santos Orientos No. 1 and Dullingari No.1 wells near the Queensland/South Australia border and the Smart Oil Orient No. 2 well on the Grey Range.
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Current geological surface mapping of the Officer Basin, W.A., by BMR has given an incomplete picture because the area is largely covered by flat-lying Permian fluvioglacials or lateritized Cretaceous rocks and the outcrops give no indication of the structure and composition of the sediments in most of the basin. The geological boundaries within the basin and at its margins are ill-defined, and the only reliable shallow subsurface information available from geophysical and well data is along the northern part of the basin near Warburton Mission. A seismic survey in the Officer BaSin, W.A., is planned to operate from mid-July to December 19720 The survey is to be conducted along a NE-SW line roughly following the road between Lake Throssell and Warburton Mission at the two margins of the basin. It will consist of a series of combined refraction and reflection probes located along the road. The operations will start with two probes near the centre of the basin, and the location of subsequent probes will depend on the progressive assessment of results. The results will be tied to those from the earlier seismic surveys in the northern part of the basin.
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<p>This is a Joint Research Project of a seismic test survey using dynamite as a seismic source in the Gippsland Basin between South Australian Gas Company (SAGASCO) and Geoscience Australia. This survey wad conducted by using the GA Sercel SN368 seismic 120 channel data acquisition system, two drilling rigs and seismic crew. The primary objective of the seismic test survey was to test whether by using dynamite as the seismic energy source, seismic reflection events could be recorded from geological horizons below the base of the Latrobe Valley Group. Processing of the seismic data revealed that using explosives as a seismic source also had difficulty in resolving seismic reflection events below the Labtrobe Valley Group sediments. In places multiple reflection events due to the coal beds within the Latrobe Valley Group are intermixed with primary reflections making interpretation of deeper reflection events difficult or impossible. However long offsets recordings highlighted a significant first break refraction event at far offset distances, which from preliminary interpretations is related to the base of the Latrobe Valley Group or top of Strzelecki Group. To resolve the thickness of Strzelecki Group sediments, the recording of first break refraction events using long offset walkaway spreads (offsets in the 6 to 8 km range) maybe a technique to test in future seismic surveys.<p><b>Raw data for this survey are available on request from clientservices@ga.gov.au - Quote eCat# 74946</b>
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The Geoscience Australia Onshore Seismic GIS layer is layer showing the locations of Onshore Seismic Survyes carried out by Geoscience Australia and it's predecessors, Australian Geological Survey Organisation (AGSO) and the Bureau of Mineral Resources (BMR). The layer contains URL link to free downloadable data. The data includes processed data in SEGY format. The metadata includes acquisition reports, processing reports, processed images and so on. The data acquisition was carried out in Australia from 1949 to present by Geoscience Australia and various partners such as State and Geologcial Survey Organisations. The set of reflection and refraction data comprises over 12,000 km of coverage, and provides an insight into the variations in crustal architecture in the varied geological domains.