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  • Presentation slides and speaking notes are provided for a presentation that was given online on Wednesday 7th October 2020, 11:00 to 12:00 AEDT time (UTC +11). The presentation coincided with the release of two products; (1) a new web page for the Australian Fundamental Gravity Network (AFGN), and (2) the 2019 Australian National Gravity Grids (eCat Record 133023). Not mentioned as a separate item, the presentation drew heavily on material in the Explanatory Notes for the gravity grids (eCat Record 144233) which was also released on this day. The presentation was pitched at the level of a general audience. It commenced with an introduction to gravity, and how it changes from one place to another in step with different geological units. The subjects of 2-dimensional digital grids and how coloured images are derived from them were then covered as a prelude to later material. The speakers then described first of the two main topics - the Australian Fundamental Gravity Network (AFGN) and its importance when producing the 2019 Australian National Gravity Grids. The AFGN is a series of gravity benchmarks that allow gravity surveys to be linked to the Australian Absolute Gravity Datum 2007 (AAGD07). This makes it possible for the many separate gravity data sets that have been acquired in Australia to be combined into a seamless whole. Gravity data from 1308 ground surveys and 14 blocks of airborne gravity and airborne gravity gradiometry have been combined with offshore gravity data from satellite altimetry to form the 2019 Australian National Gravity Grids. This marks the first time that airborne data have been incorporated into the national gravity grids. It is also the first time that the offshore data have been fully processed alongside the onshore data. Grids of three types of gravity anomalies were produced; Free Air Anomaly (FAA), Complete Bouguer Anomaly (CBA), and De-trended Global Isostatic Residual (DGIR). During the presentation, various comparisons were made illustrating the improvements made with the 2019 grids in comparison with the previous 2016 grids and the benefits of incorporating airborne data into the grids. The gravity grids were produced to assist those involved in geological mapping and exploration, and it is hoped that the new grids will inspire users to revisit their geological interpretations and to aid explorers to identify new opportunities and to more efficiently focus their efforts on prospective ground. The presentation was recorded, and the recording of the presentation is available on demand on the Geoscience Australia YouTube Channel at https://youtu.be/3CyqrqBM0xg. Introductions were made by Marina Costelloe. The event was controlled by Chris Nelson, and the recording was edited by Douglas Warouw. Note that there are some minor differences between the presentation material given here and the presentation seen in the video recording. These changes were made in the interest of clarity and include the removal of “animation” effects and the provision of some additional text. Speaker Biography for Richard Lane; Richard joined Geoscience Australia in 2001 after a career as a mineral and petroleum geophysicist with CRA Exploration / Rio Tinto and as the Program Leader responsible for the development of the TEMPEST AEM system in CRC AMET. As a Senior Geophysicist in the Geophysical Acquisition and Processing Section, he has been evaluating the role of airborne gravity and airborne gravity gradiometry on a national scale. He is an ASEG Gold Medal recipient, a Society of Exploration Geophysicists Honorary Lecturer, and a Distinguished Geoscience Australia Lecturer. Speaker Biography for Phillip Wynne; Phillip has been with GA for over twenty years. In that time, he has been involved in all aspects of regional gravity surveys. He currently oversees gravity surveys conducted by GA and Australian States and Territories and manages the Australian Fundamental Gravity Network.

  • This flythrough shows the seafloor bathymetry, cores and canyon names for the Sabrina slope region of East Antarctica. Indigenous names for canyons were proposed following consultation with the Noongar people in Western Australia, the region of Western Australia that was formerly conjugate to the Sabrina margin. Canyon names are as follows: 1. Boongorang Canyon (Blowing in the wind) 2. Manang Canyon (Pool of Water Canyon) 3. Maadjit Canyon (Water Serpent Canyon) 4. Jeffrey Canyon (after Shirley Jeffrey, diatom researcher) 5. Morka Canyon (Winter Canyon) 6. Minang-a Canyon (Whale Canyon)

  • Have you ever wondered what lava looks like when it cools down? This short video introduces rocks from volcanoes and their features using some of the samples in the Geoscience Australia Education Centre. Viewers are shown different types of lava rock, bombs, obsidian and pumice. The video is suitable for middle primary and older students as well as a general audience; it introduces some technical terms and uses samples available for school students to handle during visits to the Centre.

  • Australia is a unique continent. This short video introduces the physical geography of Australia using a colourful topographic map. Viewers are shown the three major physical regions of the continent, the lack of large mountains and consider why relatively few people live in Australia given its size.

  • The 2018 revision of Australia's National Seismic Hazard Assessment (NSHA18) represents a substantial improvement from the 2013 NSHA. In particular, this revision will include a fault source models, an improved and more homogeneous earthquake catalogue, and greater epistemic uncertainty through a call for third party source models. This paper presents updated models of seismicity and ground motion that are currently being developed at Geoscience Australia for the NSHA. We use the OpenQuake software to calculate seismic hazard for Australia and compare with OpenQuake implementations of third-party models and the 2013 NSHA. Weighting of logic tree branches for alternative models are discussed, and how these relate to the fundamental datasets on which they are based. A smoothed seismicity model is developed based on recent seismicity while source models derived from neotectonic fault data consider a much longer time history. Final weightings, including for third party models, will be determined in consultation with members of the Australian seismological community.

  • Probabilistic methods applied to infrequent but devastating natural events are intrinsically challenging. For tsunami analyses, a suite of geophysical assessments should be in principle evaluated because of the different causes generating tsunamis (earthquakes, landslides, volcanic activity, meteorological events, asteroid impacts) with varying mean return times. Probabilistic Tsunami Hazard Analyses (PTHAs) are conducted in different areas of the world at global, regional, and local scales with the aim of assessing and mitigating tsunami risk and improving the early warning systems. The PTHAs enhance knowledge of the potential tsunamigenic threat by estimating the probability of exceeding specific characteristics of the tsunami intensities (e.g. run-up or maximum inundation heights) within a certain period of time (exposure time) at given locations (target sites); these estimates can be summarized in hazard maps or hazard curves. This discussion presents a broad overview of PTHA, including: (i) sources and mechanisms of tsunami generation, emphasizing the variety and complexity of the tsunami sources and their generation mechanisms; (ii) developments in modelling the propagation and impact of tsunami waves; (iii) statistical procedures for tsunami hazard estimates that include the associated epistemic and aleatoric uncertainties. Key elements in understanding the potential tsunami hazard are discussed, in light of the rapid development of PTHA methods during the last decade and the globally distributed applications, including the importance of considering multiple sources, their relative intensities, probabilities of occurrence and uncertainties in an integrated and consistent probabilistic framework.

  • Unique challenges are faced in modelling faults in intraplate regions for seismic hazard purposes. Low fault slip rates compared to landscape modification rates lead to often poor discoverability of fault sources, and favours incomplete characterisation of rupture behaviours. Irrespective, regional and local test cases have demonstrated that fault sources assigned activity rates consistent with paleoseismic observations have the potential to significantly impact probabilistic seismic hazard assessments in Australia. To reflect this, the 2018 Australian NSHA will for the first time incorporate a fault source model. The model includes over 300 onshore faults, and a handful of offshore faults, which are modelled as simplified planes and assigned a general dip and dip direction. Dips are obtained from seismic-reflection profiles, where available, or inferred by taking into account surface geology and geomorphology, or other fault geometries within similar neotectonic settings. The base of faulting is generally taken as the regional maximum depth of distributed seismicity. Slip rates are calculated from displaced strata of known age, estimated from surface expression, or are extrapolated from other faults within similar neotectonic settings. We construct logic trees to capture epistemic uncertainty in fault source parameters, including magnitude frequency distribution, and the potential for random, periodic or episodic recurrence behaviour. This presentation introduces the new fault source database, the fault source logic tree as it currently exists, and discusses uncertainty in and sensitivity to various elements of the proposed fault source input model.

  • How do some of the rocks in Minecraft form and behave in real life? This short video discusses bedrock, obsidian and redstone using real rock samples and references to the game. Two posters provide further information about the geology of Minecraft and are available from https://ecat.ga.gov.au/geonetwork/srv/eng/catalog.search#/metadata/79560 For more education resources visit ga.gov.au/education

  • Understanding disaster risk enables Government, industry and the community to make better decisions on how to prepare for disasters and improve the resilience of communities. Geoscience Australia develops and provides fundamental data and information to understand disaster risk so that we can determine how hazards impact the things that are valuable to us.

  • Understanding disaster risk enables Government, industry and the community to make better decisions on how to prepare for disasters and improve the resilience of communities. Geoscience Australia develops and provides fundamental data and information to understand disaster risk so that we can determine how hazards impact the things that are valuable to us. Through robust and proven methodologies, technical expertise and trusted data, our national capability can support informed decisions to prepare for and respond to hazard events so that the impact of disasters can be reduced, and to inform where and how our future communities and supporting infrastructure are built.