In 2011, Geoscience Australia collected 484 km of deep-crustal (22 second) seismic reflection data. The survey (11GA-YO1) traverses the north-eastern edge of the Yilgarn Craton, the Officer Basin and the western end of the Musgrave Province. The purpose of the seismic survey was to delineate broad crustal architecture and define the Moho, with particular interest in the Yilgarn-Musgrave boundary. To compliment the seismic survey, a 3D geological model was constructed that incorporates interpretations derived from seismic, potential field, surface geology and borehole data. Forward and inverse modelling techniques were applied to the potential field data to extrapolate the seismic interpretations into 3D space. Borehole data was used to constrain the interpretation of upper crustal sequences where available. The model was later used to constrain 3D potential field inversions of the area. This poster presents a 3D geological model of the YOM region as well as the geological and geophysical constraints that were used to construct it. Some of the fundamental and technical limitations of the model are also discussed.

The first RSTT model for Australia has been developed based on the Australian Seismological Reference Model (AuSREM) that was released in late 2012. The densely-gridded P and S wave distributions of the crust and upper mantle of AuSREM have been simplified and translated into the 7 layer crustal and upper mantle RSTT model. Travel times computed with this RSTT model are evaluated against travel times computed in full 3D through the AuSREM model to assess the impact of the approximations used by RSTT. Location estimates of 5 ground truth earthquakes (GT1, GT2 and GT5) using the global ak135 reference model, the RSTT model and the full 3D travel times are compared. It is found that the RSTT model can reproduce the 3D travel times fairly accurately within its distance of applicability, thereby improving location estimates compared to using a global travel time model like ak135. However the benefit of using RSTT for locating Australian earthquakes is far less than using full 3D travel times, mainly because most stations tend to be further away from the source than the distance of RSTT applicability.

Four posters describing work being undertaken in Antarctica: VULNERABLE MARINE ECOSYSTEMS IN ANTARCTICA SEABED MAPPING IN ANTARCTICA DEFINING ABSOLUTE GRAVITY AN ANTARCTIC GEODESY

The recently released ISC-GEM catalogue was a joint product of the International Seismological Center (ISC) and the Global Earthquake Model (GEM). In a major undertaking it collated, from a very wide range of sources, the surface and body wave amplitude-period pairs from the pre digital era; digital MS, mb and Mw; collated Mw values for 970 earthquakes not included in the Global CMT catalogue; used these values to determine new non-linear regression relationship between MS and Mw and mb and Mw. They also collated arrival picks, from a very wide range of sources, and used these to recompute the location, initially using the EHB location algorithm then revised using the ISC location algorithm (which primarily refined the depth). The resulting catalogues consists of 18871 events that have been relocated and assigned a direct or indirect estimate of Mw. Its completeness periods are, Ms - 7.5 since 1900, Ms - 6.25 1918 and Ms - 5.5 1960. This catalogue assigns, for the first time, an Mw estimate for several Australian earthquakes. For example the 1968 Meckering earthquake the original ML, mb and MS were 6.9, 6.1 and 6.8, with empirical estimates of Mw being 6.7 or 6.8. The ISC-GEM catalogue assigns an Mw of 6.5. We will present a poster of the Australian events in this ISC_GEM catalogue showing, where available, the original ML, mb, Ms, the recalculated mb and Ms, and the assigned Mw. We will discuss the implications of this work for significant Australian earthquakes.

Displayed at Questacon July 21-22

Homogeneity Tests for a Rotary Sample Divider Two rock types, a coarse-grained granite and a finer-grained volcanic rock, were used to test a Rotary Sample Divider attached to a Rocklabs Boyd Crusher for homogeneity. Approximately 3kg of each rock type were broken down by a jaw crusher, and then processed through a Boyd Crusher with splits taken using the attached rotary sample divider. The formula 10/(100-(10*n))-where n=the number of the split-was used to process the entire sample, i.e., 10% of the first split was taken and remainder returned to the Boyd crusher; 11% of the second split taken and remainder returned to the crusher; 12.5% of the 3rd one taken and remainder returned to the Boyd crusher etc., until all the sample was used and there were 10 roughly equal splits. Each split was halved and each half pulverised for 3 minutes in a Tungsten Carbide ring mill for 3 minutes. Pressed powder pellets and Lithium Borate glasses were made and analysed using a PW2404 XRF spectrometer. Results of major and trace element analysis shows that there is no apparent bias between either individual splits or from the first split to the last split, indicating homogeneity was achieved using the rotary sample divider.

Poster prepared for International Association of Hydrogeologists Congress 2013 Sonic drilling is a relatively new technology that was used successfully to obtain relatively uncontaminated and undisturbed continuous core samples with excellent (>99%) recovery rates to depths of 206m in unconsolidated fluvio-lacustrine sediments of the Darling River floodplain. However, there are limitations with the standard sonic coring method. Sands, in particular, are disturbed when they are vibrated out of the core barrel into the flexible plastic sampling tube. There can be changes to moisture content, pore fluid chemistry and sediment mineralogy on exposure to the atmosphere, even when the samples are processed and analysed soon after collection. The option exists during sonic drilling to encapsulate the core in rigid polycarbonate lexan tubes. Although this increases costs and reduces drilling rates, atmospheric exposure of the core during drilling is reduced to the ends of the lexan tubes before being capped. In addition, the tubes can be purged with an inert gas such as argon. Lexan coring is best carried out below the watertable as the heat from drilling dry clays can cause the polycarbonate to melt. In the study, 60 sonic holes (4.5 km) and 40 rotary mud holes (2 km) were obtained as part of a program to map and assess potential groundwater resources and managed aquifer recharge (MAR) targets over a large area (7,500 km2) of the Darling River floodplain. Two of the sonic bores were drilled to depths of 60 metres to obtain lexan-encapsulated core samples. These cores were used to obtain less perturbed samples for pore fluid analysis (salinity, major ions, trace metals, stable isotopes), textural analysis, and analysis of mineral phases to help assess aquifer clogging potential (using XRD, XRF, SEM). An additional advantage of the lexan coring was the recovery of encapsulated and intact sediment intervals for determining porosities, effective porosities, hydraulic conductivities, and other geophysical and petrophysical measurements. By painting some tubes black, sand samples were also successfully obtained for optically stimulated luminescence (OSL) dating. Alternatively, opaque black lexan can be made to order by the supplier. Overall, the superior sample integrity obtained from lexan coring enables a greater range of hydrogeological and hydrochemical parameters to be assessed.

Poster accepted to the Australian Science Communication Conference 2014 Abstract: EarthSci is a powerful new tool for visualising earth science datasets in four dimensions. This 'Virtual Earth'-style software platform was originally developed by Geoscience Australia to assist its researchers describe, understand and present their findings. As demand for accessible data visualisation has increased, the tool has been redeveloped to increase its stability, useability and flexibility as a presentation and promotional tool. Importantly, EarthSci allows underground features such as groundwater, stratigraphy, mineral systems and faults to be visualised together with surface features such as topography, land cover and satellite data. Presenting them together in a single visualisation environment enables powerful stories about the history, evolution and geophysical construction of our continent to be told. This ability makes EarthSci stand out from other virtual globe environments. The latest version of the tool is designed to be shared, with features that support the visualisation of many different data formats, an in-built animation function that enables fly-throughs to be generated from within the tool and a presentation mode that enables journeys through the virtual globe environment to be constructed. Due to be launched in the first half of 2014, EarthSci is a fully customisable software package that is freely open to developers in any field. Geoscience Australia welcomes collaboration with all those who may be interested in extending its use as a scientific, communication and visualisation tool.

The Frome airborne electromagnetic (AEM) survey (Figure 1) is the largest of three regional AEM surveys flown under the 5-year Onshore Energy Security Program (OESP) by Geoscience Australia, and the largest survey by area ever flown in Australia. The aim of the survey is to reduce risk and stimulate exploration investment for uranium by providing reliable pre-competitive data. The Frome AEM survey was released with two different Geoscience Australia layered earth inversions (GA-LEI): a sample-by-sample inversion (SBS GA-LEI) to enhance vertical features; and, a line-by-line inversion (LBL GA-LEI) to enhance horizontal features (see Hutchinson et al. 2010). A separate depth of investigation was calculated for each inversion using a method modified after Christiansen and Auken (2010) for the SBS inversion and Oldenburg and Li (1999) for the LBL inversion. A range of data products were produced including point-located ASCII data, georeferenced conductivity sections and grids, PDF multiplots, GOCAD surfaces and ancillary data. A range of under-cover features are mapped in the conductance image (Figure 1), including (but not limited to): extensions to known palaeovalley networks in the Frome Embayment; the under-cover extent of the Benagerie Ridge; regional faults in the Frome Embayment and Murray Basin; folded and faulted Neoproterozoic rocks in the Adelaide Fold Belt; Cenozoic - Mesozoic stratigraphy in the Frome Embayment; neotectonic offsets in the Lake Eyre Basin; conductive Neoproterozoic rocks associated with copper-gold mineralisation; and, coal-bearing structures in the Leigh Creek area, as well as groundwater features. A depth of investigation (DOI - depth of reliable signal penetration) of up to 400 m is calculated in areas of thin cover and resistive basement, e.g., Adelaidean rocks in the Olary Ranges (Figure 2). In Cenozoic - Mesozoic sediments in the Frome Embayment and the Murray Basin the DOI is about 100-150 m, decreasing to less than 50 m under the salt lakes. The Frome AEM data set is available for free download from Geoscience Australia: http://www.ga.gov.au/minerals/projects/current-projects/airborne-electromagnetics.html For more information contact: Dr Ian Roach Continental Geophysics, Geoscience Australia Ian.Roach@ga.gov.au

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