In 1999, a grid of five deep seismic reflection traverses was acquired within an area approximately 50 km wide by 50 km long in the Kalgoorlie Region, Eastern Goldfields Province, Yilgarn Craton. The grid tied into the existing 1991 deep seismic reflection transect (EGF1) and the 1997 high resolution and regional seismic profiles acquired by the Australian Geodynamics Cooperative Research Centre (AGCRC) and Kalgoorlie Consolidated Gold Mines (KCGM). The data were acquired to examine the geometry of the major structural features of the region, particularly the highly mineralised Bardoc Shear, and to provide three-dimensional information on granites-greenstones relationships. This paper describes the geometry of the crust and, in particular, the geometry of the granite and greenstones above the prominent regional detachment surface that occurs at about 4-6 km depth, though in one place it may extend to a depth of approximately 11 km. From the seismic, the Bardoc Shear is confirmed as west dipping and a non-planar crustal penetrating structure. The gravity modelling suggests that there is no need for the large volumes of mafic or ultramafic material previously assumed to be at depth, apart from those mapped at the surface and projected to depth.

Labuan Basin lies in deep water adjacent to the eastern Kerguelen Plateau. The basin is about 800 km long and 300 km wide and contains up to 4.5 km of sediment. A general lack of geophysical data and geological samples in this remote basin have inhibited understanding of its stratigraphy and crustal origin. Our new seismic stratigraphic interpretation of the Labuan Basin is based on deep multichennel seimic data collected by Geoscience Australia in 1997 during "Rig Seismic" surveys 179 and 180 intergrated with results of Ocean Drilling Program (ODP) Leg 183 (1998-1999)

Seismic line 07GA-IG2, described here, forms part of the Isa-Georgetown-Charters Towers seismic survey that was acquired in 2007. The seismic line is oriented approximately east-west and extends from east of Croydon in the west to near Mt Surprise in the east (Figure 1). The acquisition costs for this line were provided jointly by the Geological Survey of Queensland and Geoscience Australia, and field logistics and processing were carried out by the Seismic Acquisition and Processing team from Geoscience Australia. Three discrete geological provinces have been interpreted on this seismic section (Figure 2). Two of these, the Numil and Abingdon Provinces, only occur in the subsurface. The upper crustal part of the seismic section consists of the Paleo- to Mesoproterozoic Etheridge Province, which here includes the Croydon Volcanic Group in the western part of the Province. In this east-west profile, the crust is essentially two-layered, with a strongly reflective lower crust defining the Numil and Abingdon Provinces and a less reflective upper crust being representative of the Etheridge Province.

Potential field data were used to constrain or support the geological interpretations of the 2006 and 2007 North Queensland seismic data. Potential field forward modelling, potential field inversions and worms of potential field data all supported the interpretations of the seismic data.

A ~400 km long deep crustal reflection seismic survey across central Victoria, Australia, was carried out in 2006 as a collaborative project between the pmd*CRC, Geoscience Australia, the Victorian Government, Ballarat Goldfields NL, Gold Fields Australasia Pty Ltd and Perseverance Corporation Ltd, using the facilities of the National Research Facility for Earth Sounding (ANSIR). The aim was to cross several Neoproterozoic-Palaeozoic basement zones and provide information on the crustal architecture, particularly across the highly prospective Palaeozoic rocks occurring along strike to the north of the major Victorian goldfields, such as Bendigo. In the west, the Moyston Fault is a major east-dipping planar fault near the eastern edge of the Grampians-Stavely Zone, which was probably the eastern margin of continental Australia in the Cambrian. It cuts through the entire crust to the Moho. The Stawell Zone, immediately east of the Moyston Fault, has the geometry of a doubly vergent wedge. The boundary between the Stawell Zone and the Bendigo Zone farther to the east is the Avoca Fault, which appears to be a west-dipping listric fault that links to the Moyston Fault at a depth of about 22 km, forming a Y-shaped geometry. Internal faults in the Stawell and Bendigo zones are almost entirely west-dipping listric faults, which cut deep into the highly reflective lower crust, interpreted to be stacked ? Cambrian oceanic crust. Previous models advocating the presence of a mid-crustal detachment are not supported by these deep crustal scale faults. The boundary between the Bendigo and Melbourne zones, the Heathcote Fault Zone, forms a zone of strong west-dipping reflections about three kilometres wide to a depth of at least 20 km, and possibly to the Moho. The fault zone is complex and contains a boninite-tholeiite association along with blueschists in a serpentinite-matrix melange, and oceanic sedimentary rocks. The Melbourne Zone contains a deformed sedimentary pile up to 15 km thick, and contains previously unrecognised north-dipping listric faults, interpreted to be thrusts. The Governor Fault separates the Melbourne Zone from the Tabberabbera Zone and contains similar rocks to the Heathcote Fault Zone. Near the surface, the Governor Fault dips to the north at about 10°. The seismic character of the lower crust below the Melbourne Zone (the "Selwyn Block") is significantly different to that observed below the Bendigo and Stawell zones, and consists of several very strong subhorizontal reflections about 5-6 km thick starting at about 18 km depth, with a less reflective zone below it. In summary, the deep seismic data across central Victoria has allowed the geometry of the rocks and structures mapped at the surface to be projected through the entire crust, thus providing important constraints to test previous tectonic models.

Chapter in Geoscience Australia Record for the Northern Yilgarn Seismic Workshop

In 2008, as part of its Onshore Energy Security Program, Geoscience Australia and PIRSA acquired 262 km of vibroseis-source, deep seismic reflection data as a single north-south traverse (08GA-C1) in the Curnamona Province in South Australia. This line started in the south near outcrop of the Willyama Supergroup, ran to the east of Lake Frome along the Benagerie Ridge, and ended in the north to the northeast of the Mount Painter and Mount Babbage Inliers. Almost the entire route of the seismic traverse was over concealed bedrock, with only a few drillholes which could be used as control points. Overall, the crust imaged in the seismic section is relatively reflective, although the central part of the section contains an upper crust which has very low reflectivity. The lower two-thirds of the crust contain strong, subhorizontal reflections. The Moho is not sharply defined, but is interpreted to occur at the base of the reflective package at about 13 s two-way travel time (TWT), about 40 km depth. The highly reflective crust can be tracked, from the southern end of the seismic section, northwards for a distance of about 200 km. In the north, where rocks of the Mount Painter and Mount Babbage Inliers are exposed close to the section, the crust has a marked lower reflectivity, compared to the rest of the line. This contrast in crustal reflectivity suggests that the crust beneath the Mount Painter region is different to that beneath the Willyama Supergroup of the Curnamona Province in the south, raising the possibility of an ancient crustal boundary between the two regions.

Field tests were conducted on 11 March 1974 in Waiaal Victoria to compare the seismic efficiency of Molanite, TNT, and-Anzite Blue. Ueismic energy p:enerated by equal amounts of each explosive was recorded in identical conditions, and the amplitudes of the refracted and reflected waves were measured and compared. The comparisons indicated that Molanite and Anzite Blue were equally efficient whereas TNT was about 10 percent less efficient. No significant difference was observed in the character of the seismic energy generated by any of the explosives tested.

No abstract available

In hard rock regions, a large range of stacking velocities is required to correctly stack reflectors of different dips. Typically, horizontal reflectors stack at 6000 m/s, whereas reflectors with dips of 60 degrees stack at 12,000 m/s. For high fold (vibrator) data, correct stack of conflicting dips can be achieved by dip moveout (DMO) correction. However, for lower fold (dynamite) data, the sparse offset distribution complicates application of DMO. An alternative technique involves producing stacks with different stacking velocities and stacking these stacks. This technique was applied to two seismic reflection data sets, low fold dynamite from Broken Hill and high fold vibrator data from the Lachlan Fold Belt. The Lachlan data set was used as both full 60/120 fold and reduced 10/20 fold. Velocity analysis, both analytical and empirical, was carried out to determine the range of stacking velocities. Stacking velocity increases with dip angle (cos-1 theta), but the velocity range across which an event stacks coherently increases more rapidly (approximately cos-3 theta for velocities typical of hard rock)). The most critical area for analysis is the first two seconds of data, due to greater sensitivity of NMO to stacking velocity. The optimum number of stacks is an important consideration, based on the number of stacks in which an event contributes coherently to the sum The Broken Hill stack data showed simultaneous imaging of horizontal and dipping events. For the Lachlan reduced fold data set, horizontal and moderate to steeply dipping events were stacked successfully, although not as well as the post-DMO stack of the full fold data. The technique has some problems at the shallowest levels, where the stack can be degraded due to time shifts of events in the individual stacks.