Poster/Image
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This poster shows earthquakes occurring in Australia in 2012 with a background of earthquakes occurring in Australia over the past 10 years. Also included are images produced as part of the analysis of the Ernabella, Moe and Tamworth Earthquakes as well as the yearly summary of earthquake occurrences in Australia.
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Poster linked to Abstract in Geocat# 74763 West Australian Basins Symposium, 18-21 August 2013
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Joining Geoscience Australia's Graduate Program is an exciting opportunity to learn about the diverse earth science disciplines work for the nation's leading government geoscience research and information agency. Posters and Flyers.
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Studies of earthquake source characterization are often undertaken using the back-projection technique and large, dense seismic arrays. Combinations of such arrays have also been utilised in an attempt to increase the spatial resolution of the source energy distribution patterns. However our tests show that the use of few well selected seismic stations can produce comparable results to those obtained by the processing of large seismic arrays. Employing dense arrays of seismic stations may increase the signal to noise ratio, but this is not the reason behind apparent improvements in resolution of radiated energy patterns. In practice, resolution of the source energy radiation pattern relies on the same principles as those which underline earthquake hypocentre location. Back-projection techniques applied to large Mw > 7 subduction earthquakes shows that starting with small numbers of spatially separated seismic stations the correct distribution of radiated energy can be estimated. The set of spatially separated seismic stations can be selected by the same criteria as those used for accurate hypocentral location to map radiated seismic energy not only in a plane but in 3D as well. Application of this algorithm to a number of deep (>100km) earthquakes, such as the Mw 8.2 Sea of Okhotsk event, shows the further potential of the back-projection technique.
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Poster presented at JAXA ALOS-2 1st PI workshop in Tsukuba, Japan, 19-20 September 2013
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Poster prepared for International Association of Hydrogeologists Congress 2013 Surface-groundwater interactions are often poorly understood. This is particularly true of many floodplain landscapes in Australia, where there is limited mapping of recharge and discharge zones along the major river systems, and only generalised quantification of hydrological fluxes based on widely spaced surface gauging stations. This is compounded by a lack of temporal data, with poor understanding of how surface-groundwater interactions change under different rainfall, river flow and flood regimes. In this study, high resolution LiDAR, in-river sonar, and airborne electromagnetic (AEM) datasets (validated by drilling) have been integrated to produce detailed 3-dimensional mapping that combines surface geomorphology and hydrogeology. This mapping enables potential recharge zones in the river and adjacent landscape to be identified and assessed under different flow regimes. These potential recharge zones and groundwater flow pathways were then compared against the spatial distribution of discontinuities in near-surface and deeper aquitard layers derived from the AEM interpretation. These 3D mapping constructs provide a framework for considering groundwater processes. Hydrochemistry data, allied with hydraulic data from a bore monitoring network, demonstrate the importance of recharge during significant flood events. In many places, the AEM data also affirm the spatial association between fresher groundwater resources and sites of river and floodplain leakage. At a more localised scale, hydrogeochemical data allows discrimination of lateral and vertical fluxes. Overall, this integrated approach provides an important conceptual framework to constrain hydrogeological modelling, and assessments of sustainable yield. The constructs are also invaluable in targeting and assessing managed aquifer recharge (MAR) options.
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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.
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Poster showing significant meteor impact sites in Australia
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Papua New Guinea lies in a very active volcanic region of the world, where eruptions and other volcanic hazards can have disastrous results. To monitor the volcanoes, the Rabaul Volcanological Observatory (RVO) was established in 1940. Geoscience Australia has provided the RVO with technical aid in many forms, including (since 2010) advice and assistance in the creation of an information management system (IMS). The purpose, scope and design features of this system are described.
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Poster prepared for International Association of Hydrogeologists Congress 2013 In this study, a multi-disciplinary systems mapping approach has completely revised our understanding of the age, stratigraphy, mode of deposition and landscape evolution of Lower Darling Valley (LDV) sediments within the north-western Murray Basin. The Cenozoic sequence in this area contains Paleogene and Neogene shallow marine, fluvial and shoreline sediments overlain by Quaternary lacustrine, aeolian and fluvial units. The surficial Quaternary fluvial units of the valley form a complex group of morphostratigraphic units which vary in their distribution, character and geomorphic expression through the study area. Resolving the distribution of these units has been particularly important for understanding surface-groundwater interactions. In the LDV Quaternary fluvial sequence, multiple scroll-plain tracts are incised into higher, older more featureless floodplains. Prior to this study, these were respectively correlated to the Coonambidgal and Shepparton Formations of the Riverine Plain in the eastern Murray Basin and associated with the subsequently discarded Prior Stream/Ancestral River chronosequence of different climatically controlled depositional styles. In contrast to that proposition, we ascribe all LDV Quaternary fluvial deposition to lateral-migration depositional phases of one style, though with more variable stream discharges and channel and meander-scroll dimensions. Successively higher overbank-mud deposition through time obscures scroll traces and provides the main ongoing morphologic difference. A new morphostratigraphic unit, the Menindee Formation, refers to the mostly older and higher floodplain sediments, where scroll traces are obscured by overbank mud which continues to be deposited by the highest modern floods. Younger inset scroll-plain tracts, with visible scroll-plain traces, are still referred to the Coonambidgal Formation. Another new stratigraphic unit, the Willotia beds, refers to even older fluvial sediments, now above modern floodplain levels and mostly covered by aeolian sediments. This work provides important insights into the nature of Australian Quaternary fluvial deposition, with important implications for hydrogeological processes, groundwater resources and the assessment of managed aquifer recharge options.