<div>The Australian Bureau of Meteorology (BoM), Geoscience Australia (GA) and the Pacific Community (SPC) work together on the Australian Aid funded Pacific Sea Level and Geodetic Monitoring Project (PSLGMP). The project is focused on determining the long-term variation in sea level through observation and analysis of changes in the height of the land (using Global Navigation Satellite System (GNSS) data) and changes in the sea level (using tide gauges managed and operated by the BoM. It is the role of GA and SPC to provide information about ‘absolute’ movement of the tide gauge (managed by BoM) using GNSS to continuously monitor land motion and using levelling (SPC) to measure the height difference between the tide gauge and GNSS pillar every 18 months. </div><div>Land movement caused by earthquakes, subsidence and surface uplift have an important effect on sea level observations at tide gauges. For example, a tide gauge connected to a pier which is subsiding at a rate of 5 mm per year would be observed as a rate of 5 mm per year of sea level rise at the tide gauge. Because of this, it is important to measure, and account for, the movement of land when measuring ‘absolute’ sea level variation - the change in the sea level relative to the centre of the Earth. Relative sea level variation on the other hand is measured relative to local buildings and landmass around the coastline.</div><div>Geoscience Australia’s work enables more accurate 'absolute' sea level estimates by providing observations of land motion which can be accounted for by BoM when analysing the tide gauge data.</div><div><br></div>

<div>Mineral prospectivity studies seek to map evidence of mineral system activity, with the aim of informing mineral exploration decisions and guiding exploration in the face of uncertainty. These studies leverage the growing volumes of information that are available to characterise the lithosphere by compiling covariate (or feature) grids that represent key mineral system ingredients. Previous studies have been categorised as either “knowledge-driven” or “data-driven” approaches depending on whether these grids are integrated via expert elicitation or by the empirical relationship to known mineralisation, respectively. However, to our knowledge, the underlying modelling framework and assumptions have not been systematically reviewed to understand how choices in the approach to the problem influence modelling outcomes. Here we show the broad mathematical equivalence in these approaches and highlight the limitations inherent when optimising to minimise misfit in potentially under-determined problems. We argue that advances in mineral prospectivity are more likely to be driven by careful consideration of the model selection problem. Focusing effort on model selection will not only drive more robust mineral prospectivity predictions but may also simultaneously refine our understanding of key mineral system processes. To build on these results, we present the Mineral Potential Toolkit; a software repository to facilitate feature engineering, statistical appraisal, and quantitative prospectivity modelling. The toolkit enables a novel approach that combines the best aspects of previous methods. Abstract presented to the 26th World Mining Congress 2023 (https://wmc2023.org/)

<div>The integrity and strength of multi-technique terrestrial reference frames, such as realisations of the International Terrestrial Reference Frame (ITRF), depend on the precisely measured and expressed local-tie connections between space geodetic observing systems at co-located observatories. Australia has several observatories which together host the full variety of space geodetic observation techniques, including Global Navigation Satellites Systems (GNSS), Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) beacons.</div><div><br></div><div>This report documents the technical aspects of the local tie survey completed at the Mount Stromlo observatory, in Canberra in 2014. The aim of the survey was to precisely measure the local terrestrial connections between the space-based geodetic observing systems co-located at the observatory, which include 3 International GNSS Service (IGS) stations, SLR and DORIS infrastructure. In particular, this report documents the indirect measurement of the SLR invariant reference point. Geoscience Australia has routinely performed classical terrestrial surveys at Mount Stromlo, including surveys in 1999, 2002 and 2003 (post-fire). A high precision survey was conducted between the survey pillars surrounding the SLR observatory. These survey pillars were monitored to ensure their stability as part of a consistent, stable terrestrial network from which local tie connections were made to the SLR and other observing systems. The relationship between points of interest included the millimetre level accurate connections and their associated variance covariance matrix.</div><div><br></div>

<div>The annual Asia Pacific Regional Geodetic Project (APRGP) GPS campaign is an activity of the Geodetic Reference Frame Working Group (WG) of the Regional Committee of United Nations Global Geospatial Information Management for Asia and the Pacific (UN-GGIM-AP). This document describes the data analysis of the APRGP GPS campaign undertaken between the 10th and 17nd of September 2023. Campaign GPS data collected at 124 sites in nine countries across the Asia Pacific region were processed using version 5.2 of the Bernese GNSS Software in a regional network together with selected IGS (International GNSS Service) sites. The GPS solution was constrained to the ITRF2020 reference frame by adopting IGS20 coordinates on selected IGS core reference sites and using the final IGS earth orientation parameters and satellite ephemerides products. The average of the root mean square repeatability of the station coordinates for the campaign was 2.5 mm, 2.5 mm and 6.9 &nbsp;mm in north, east and up components of station position respectively.</div><div><br></div>

<div>The Pacific Islands Applied Geoscience Commission (SOPAC) requested Geoscience Australia to compute International Terrestrial Reference Frame (ITRF) coordinates for 18 survey sites on islands in the northern Fiji archipelago from continuous geodetic GPS measurements observed from 8th July to 5th August 2008 inclusive. The GPS data was processed using version 5.0 of the Bernese GPS Software in a regional network together with selected IGS sites. The GPS solution was constrained to the ITRF2005 reference frame through adopting IGS05 coordinates on selected IGS reference sites and using the final IGS earth orientation parameters and satellite ephemerides products.</div><div>These coordinates provide the coordinate reference frame to be used to define Fiji’s claim to extended continental shelf under the provisions of Article 76 of the United Nations Convention on the Law of the Sea.</div><div><br></div>

<div>This record links to tarred folders with simulation files used for a study on tsunami hazards in Tongatapu (eCat 146012) - DOI: https://doi.org/10.1093/gji/ggac140. </div><div><br></div><div>Access to this data will only be available by request via datacatalogue@ga.gov.au</div><div><br></div><div>The files were created using code here: </div><div>https://github.com/GeoscienceAustralia/ptha/tree/master/misc/monte_carlo_paper_2021. </div><div><br></div><div>This code should be read to understand the structure and contents of the tar archives. The simulation files are large and for most use cases you won't need them. First check if your needs a met via code and documentation at the link above. If the git repository doesn't include links to what you need, then it may be available in these tar archives. Contents include the datasets used to setup the model and the model outputs for every scenario. While the modelling files and code were developed by GA, at the time of writing, we do not have permission to distribute some of the input datasets outside of GA (including the Tongatapu LIDAR). </div><div><br></div><div>Access to this data will only be available by request via datacatalogue@ga.gov.au</div>

<div>A document outlining how geoscientific data can be useful for farmers and engagement tool for geoscientists interacting with farmers and pastoralists.</div>

<div>The annual Asia Pacific Regional Geodetic Project (APRGP) GPS campaign is an activity of the Geodetic Reference Frame Working Group (WG) of the Regional Committee of United Nations Global Geospatial Information Management for Asia and the Pacific (UN-GGIM-AP). This document describes the data analysis of the APRGP GPS campaign undertaken between the 11th and 17nd of September 2022. Campaign GPS data collected at 116 sites in seven countries across the Asia Pacific region were processed using version 5.2 of the Bernese GNSS Software in a regional network together with selected IGS (International GNSS Service) sites. The GPS solution was constrained to the ITRF2014 reference frame by adopting IGS14 coordinates on selected IGS reference sites and using the final IGS earth orientation parameters and satellite ephemerides products. The average of the root mean square repeatability of the station coordinates for the campaign was 2.0 mm, 2.4 mm and 7.5 mm in north, east and up components of station position respectively.</div>

<div>Offshore probabilistic tsunami hazard assessments (PTHAs) are increasingly available for earthquake generated tsunamis. They provide standardized representations of tsunami scenarios, their uncertain occurrence-rates, and models of the deep ocean waveforms. To quantify onshore hazards it is natural to combine this information with a site-specific inundation model, but this is computationally challenging to do accurately, especially if accounting for uncertainties in the offshore PTHA. This study reviews an efficient Monte Carlo method recently proposed to solve this problem. The efficiency comes from preferential sampling of scenarios that are likely important near the site of interest, using a user-defined importance measure derived from the offshore PTHA. The theory of importance sampling enables this to be done without biasing the final results. Techniques are presented to help design and test Monte Carlo schemes for a site of interest (before inundation modelling) and to quantify errors in the final results (after inundation modelling). The methods are illustrated with examples from studies in Tongatapu and Western Australia.</div> Abstract submitted/presented to the International Conference on Coastal Engineering (ICCE) 2022 - Sydney (https://icce2022.com/). Citation: Davies, G. (2023). FROM OFFSHORE TO ONSHORE PROBABILISTIC TSUNAMI HAZARD ASSESSMENT WITH QUANTIFIED UNCERTAINTY: EFFICIENT MONTE CARLO TECHNIQUES. <i>Coastal Engineering Proceedings</i>, (37), papers.18. https://doi.org/10.9753/icce.v37.papers.18

The Gaia optical astrometric mission has measured the precise positions of millions of objects in the sky, including extragalactic sources also observed by Very Long Baseline Interferometry (VLBI). In the recent Gaia EDR3 release, an effect of negative parallax with a magnitude of approximately −17 μas was reported, presumably due to technical reasons related to the relativistic delay model. A recent analysis of a 30-yr set of geodetic VLBI data (1993–2023) revealed a similar negative parallax with an amplitude of −15.8 ± 0.5 μas. Since both astrometric techniques, optical and radio, provide consistent estimates of this negative parallax, it is necessary to investigate the potential origin of this effect. We developed the extended group relativistic delay model to incorporate the additional parallactic effect for radio sources at distances less than 1 Mpc and found that the apparent annual signal might appear due the non-orthogonality of the fundamental axes, which are defined by the positions of the reference radio sources themselves. Unlike the conventional parallactic ellipse, the apparent annual effect in this case appears as a circular motion for all objects independently of their ecliptic latitude. The measured amplitude of this circular effect is within a range of 10–15 μas that is consistent with the ICRF3 stability of the fundamental axis. This annual circular effect could also arise if a Gödel-type cosmological metric were applied, suggesting that, in the future, this phenomenon could be used to indicate global cosmic rotation. <b>Citation:</b> Titov O, Osetrova A. Parallactic delay for geodetic VLBI and non-orthogonality of the fundamental axes. <i>Publications of the Astronomical Society of Australia</i>. 2024;41:e111. doi:10.1017/pasa.2024.111