From 1 - 10 / 1022
  • Natural disasters are a frequent occurrence in the Asia-Pacific region because of the combination of very dense population and very hazard-prone areas. Australia has recently been called upon to play a leadership role in responding to natural disasters, especially in recent years, with earthquakes in Pakistan and Indonesia, landslides in the Philippines, tsunami events in Indonesia and the Solomon Islands, cyclone related flooding in Papua New Guinea, and the regular occurrence of cyclones in the southwest Pacific and southeast Asia. Furthermore, there is an increasing trend in the number and size of disasters as the effects of climate change are felt and as rapid population growth and urbanisation results in increasingly large and vulnerable populations in areas exposed to natural hazards. An activity undertaken by Geoscience Australia (GA) for AusAID made a preliminary assessment of natural hazard risk across all Asia-Pacific countries. The objective was to gain a better understanding of disaster risks across the AusAID portfolio and support AusAID to better target disaster risk reduction and humanitarian response activities. This project sought to broadly identify the characteristics, frequency, location and potential consequences of rapid-onset natural hazards, including: earthquake, tsunami, landslide, flood, cyclone, flood, wildfire and volcanic eruptions. Subsequently GA has partnered with AusAID to implement programs in the Asia-Pacific region aimed at building the capacity Government agencies to assess natural hazard risk.

  • The National Geochemical Survey of Australia (NGSA) was initiated in late 2006, and details of progress were published, among others, in Caritat et al. (2009). The ultra-low density geochemical survey was facilitated by, and based on, overbank sediment sampling at strategic locations in 1186 catchments. Included in the analysis methods was a partial extraction method by the Mobile Metal Ion (MMI) technique (Mann, 2010) of sediment sampled at the depth of 0-10 cm, air-dried and sieved to <2 mm. The MMI method is based on solubilisation of adsorbed ions and potentially can provide a measure of bio-availability, as ions in natural soil pore waters are subject to solubility by solutions stronger in complexing ability than pure water, but not subject to soil phase dissolution as achieved by strong acid or total digestion methods. Of the ten elements considered essential for plant growth (Ca, Cu, Fe, K, Mg, Mn, N, P, S and Zn), only two (N and S) were not included in the 53 elements analysed after MMI extraction of the overbank samples. Comparison of a number of MMI concentrations for each element with the corresponding total analysis for the same soil samples provides an estimate of the recovery % by MMI in a similar manner to that used by Albanese (2008) to evaluate ammonium acetate-EDTA as a measure of bio-availability. Individual maps for the eight nutrients based on MMI analysis provide some very interesting and potentially useful information. For example, highest 'bio-available' Fe concentrations are not related to the Fe-rich soils and rocks of the Pilbara, but to high rainfall areas close to the coast, where processes akin to lateritisation are still taking place. The movement of Fe as Fe2+ and its subsequent oxidation to Fe3+ is not only important to agriculture, but on the east coast of Australia it has a number of environmental consequences in river systems. The distribution pattern for Mn .../...

  • For the last 50 years, Geoscience Australia and its predecessors have been collecting onshore near-vertical-incidence deep seismic reflection data, first as low fold explosive data and more recently as high fold vibroseis data. These data have been used in conjunction with other seismic data sets by various research groups to construct depth to Moho models. The Moho has been interpreted either as a strong reflector per se, or as the bottom of a reflective band in the lower crust. However the amplitude standout of the Moho can be very much dependent on the fold of the data and applied processing sequence. Some low fold explosive data was re-processed by Geoscience Australia to enhance the Moho for comparison with recent vibroseis data, in the Mt Isa province in Queensland, and in the Southern Delamerian and Lachlan Fold Belts in Victoria. Marked improvement was achieved by time-variant band-limited noise suppression of reverberations, as well as by coherency weighted common mid point stacking. Post stack migration can also improve the clarity of the Moho, provided there is enough continuity of the data to avoid migration 'smiles'. An important consideration was amplitude scaling, with a time variant automatic gain control (AGC) employed before stack, and a weighted AGC applied after stack, in order to preserve seismic character. These results demonstrate that processing and acquisition issues need to be understood in order to assess the reflective character of the Moho and indeed to interpret its location.

  • The timing and duration of metamorphic events is commonly constrained by radiometric dating using the U-Pb or 40Ar-39Ar dating methods, or a combination of both. Each dating method can be applied to a different range of minerals, and a combination of the two methods can provide more complete timing constraints than either method on its own. Comparison of radiometric ages from different isotopic systems introduces the problem of systematic uncertainties arising from uncertainty in parameters such as decay constants and the age of method-specific reference materials. Over the past decade it has been increasingly recognized that the laboratory-based determinations of the 40K decay constants, on which the 40Ar-39Ar method is based, are relatively imprecise and that the values recommended by Steiger and Jager (1977) result in a systematic offset of 40Ar-39Ar ages relative to U-Pb-derived ages by up to ~1%. This problem has been addressed by several studies over the past decade, with the most recent study (Renne et al., 2010; 2011) providing refined estimates for the 40K decay constants, and very significant improvements in precision. Paleozoic and Paleoproterozoic examples will be presented which illustrate the improvements in the accuracy and precision of 40Ar-39Ar ages calculated using the revised decay constants, and discuss the implications for studies that use a combination of U-Pb and 40Ar-39Ar data to constrain the timing and duration of metamorphic, deformation, and mineralisation events. An Excel spreadsheet is available on request that allows recalculation of 40Ar-39Ar ages and uncertainties using the revised parameters of Renne et al. (2010; 2011), provided certain minimum information has been reported with the published ages.

  • A new approach for the 1D inversion of AEM data has been developed. We use a reversible jump Markov Chain Monte Carlo method to perform Bayesian inference. The Earth is partitioned by a variable number of non-overlapping cells defined by a 1D Voronoi tessellation. A cell is equivalent to a layer in conventional AEM inversion and has a corresponding conductivity value. The number and the position of the cells defining the geometry of the structure with depth, as well as their conductivities, are unknowns in the inversion. The inversion is carried out with a fully non-linear parameter search method based on a transdimensional Markov chain. Many conductivity models, with variable numbers of layers, are generated via the Markov chain and information is extracted from the ensemble as a whole. The variability of the individual models in the ensemble represents the posterior distribution. Spatially averaging results is a form of 'data-driven' smoothing, without the need to impose a specific number of layers, an explicit smoothing function, or choose regularization parameters. The ensemble can also be examined to ascertain the most probable depths of the layer interfaces in the vertical structure. The method is demonstrated with synthetic time-domain AEM data. The results show that an attractive feature of this method over conventional approaches is that rigorous information about the non-uniqueness and uncertainty of the solution is obtained. We also conclude that the method will also have utility for AEM system selection and investigation of calibration problems.

  • Map compiled on request from AGS Native Title Case QUD6040/2001 Proclamation 6 See 2008/3111 for particulars.

  • In mid 2010 an Indonesian team of scientists and practicians published the new Indonesian probabilistic seismic hazard analysis (PSHA) map. The new PSHA map will replace the previous version from 2002. One of the major challenges in developing the new map is that data for many active fault zones in Indonesia is sparse and mapped only at the regional scale, thus the input fault parameters for the PSHA inheret unavoidably large uncertainties. Despite the fact that most Indonesian islands are teared by active faults, only Sumatra has been mapped in sufficient detail. In other areas, such as Java and Bali, the most populated and developed regions, many active faults are not well mapped and studied. These include the well known Cimandiri-Lembang fault in west Java and the Opak fault near Jogyakarta that released the destructive M6.3 Yogyakarta earthquake in 2006. This year we start a national program to systematically study major active faults in Indonesia. The study will include the acquisition of high-resolution topography and images required for detailed fault mapping, measuring geological sliprates and locating good sites for paleoseismological studies. We will also conduct GPS-campaign surveys to measure geodetic sliprates. To study submarine active faults, we will collect and incorporate bathymetry and marine geophysical data. The research will be carried out, in part, through masters and Ph.D student thesis in the new graduate study program and research center, called GREAT - CrATER (Graduate Research for Earthquake and Active Tectonics and Center for Active Tectonics and Earthquake Research), hosted by LIPI and ITB, in partnership with the Australia-Indonesia Facility for Disaster Reduction (AIFDR). In the first four years of the program we will select several sites for active fault studies, particulary faults that pose the greatest risk to society.

  • This document presents an assessment of five earthquake scenarios for Adelaide, South Australia. The earthquake scenarios occur on the Para Fault that runs beneath the Adelaide urban area and are aligned with recurrence intervals of 100, 500, 1000, 10,000 years and the maximum magnitude earthquake possible on the fault (approximately 1 in 20,000 year event). The events selected are hypothetical and are underpinned by the current understanding of the earthquake hazard in the Adelaide region.

  • Geoscience Australia is currently drafting a new National Earthquake Hazard Map of Australia using modern methods and models. Among other applications, the map is a key component of Australia's earthquake loading code AS1170.4. In this paper we provide a brief history of national earthquake hazard maps in Australia, with a focus on the map used in AS1170.4, and provide an overview of the proposed changes for the new map. The revision takes advantage of the significant improvements in both the data sets and models used for earthquake hazard assessment in Australia since the original maps were produced. These include: - An additional 20+ years of earthquake observations - Improved methods of declustering earthquake catalogues and calculating earthquake recurrence - Ground motion prediction equations (i.e. attenuation equations) based on observed strong motions instead of intensity - Revised earthquake source zones - Improved maximum magnitude earthquake estimates based on palaeoseismology - The use of open source software for undertaking probabilistic seismic hazard assessment which promotes testability and repeatability The following papers in this session will address in more detail the changes to the earthquake catalogue, earthquake recurrence and ground motion prediction equations proposed for use in the draft map. The draft hazard maps themselves are presented in the final paper.

  • This metadata sheet refers to the following three shapefiles: flight_lines_ci11.shp photo_centres_ci11.shp photo_rectangles_ci2011.shp They can all be found in the following directory: \CIGIS\orthophoto\ortho2011 Together these datasets show the flight lines flown by AAM during the 2011 aerial survey of Christmas Island, the centre of each aerial photograph taken during flight and approximate photograph extent rectangles.