The Devil’s Mountain fault is an active fault included in the 2014 USGS hazard model for Washington State. Recent neotectonic investigations have suggested that a west-northwestwards extension of the fault (the Leech River fault) has sea-bottom and onshore evidence pointing to recurrent young offsets. Accordingly, a logic tree model for the Leech River – Devil’s Mountain fault system (LRF-DMF) incorporating various fault lengths, slip rates of 0.25 mm/yr with upper and lower alternatives of 0.15 and 0.35 mm/yr, and interactions between the faults was developed and added to Canada’s 6th Generation seismic hazard model. The LRF was given a 50% chance of being active. Although the slip rate is low for an active tectonic region, the fault system passes through greater Victoria, British Columbia, and contributes to the overall seismic hazard for southernmost Vancouver Island. We calculate the hazard in greater Victoria with and without the LRF-DMF in order to estimate its effect. The hazard in downtown Victoria is already high (coming mainly from in-slab sources at short periods and the Cascadia subduction zone at long periods) and decreases slowly northwards. The hazard increment due to the LRF-DMF is quite small, even very close to the fault, and as expected its contribution to the hazard decreases away from the fault so that in Sidney at ~25 km distance it is insignificant. The importance would have been very different in a lower hazard region, or if the slip rate on the LRF-DMF had been considerably higher.

Many mapped faults in the south-eastern highlands of New South Wales and Victoria are associated with apparently youthful topographic ranges, suggesting that active faulting may have played a role in shaping the modern landscape. This has been demonstrated to be the case for the Lake George Fault, and may reasonably be inferred for the poorly characterised Murrumbidgee, Khancoban, Tantangara, Berridale Wrench and Tawonga faults. More than a dozen nearby faults with similar relief are uncharacterised. In general, fault locations and extents are inconsistent across scales of geologic mapping, and rupture lengths and slip rates and behaviours remain largely unquantified. A more comprehensive understanding of these faults is required to support safety assessments for communities and large infrastructure.

Constraints on the morphology of the Moho are essential to establish reliable models of the subsurface and infer the evolution of the Australian crust. Reliable information on crustal thickness variations is important for thermal modelling and structural mapping, for both energy and mineral system studies. Here, we combine information from both passive seismic deployments and full-crustal reflection seismic profiling to produce a new representation of the character of the Moho in northern Australia. Data coverage has been dramatically improved by investments, under the Exploring for the Future program, in new deployments of passive seismic instrumentation and expansion of the network of reflection seismic profiles in the South Nicholson and Barkly regions. Using a new approach to combining results from different classes of seismic analysis, different spatial sampling associated with the various types of data have been taken into account. The resulting Moho surface reveals small-scale features not seen in previous models. New data reveal that some Moho discontinuities are clearly associated with known structures such as the Willowra Suture. Similar ~100 km wavelength undulations are visible in areas under cover that may indicate the presence of unknown major structures. Significant base metal mineral deposits appear to be localised along the edges of thicker crustal block. <b>Citation:</b> Gorbatov, A., Medlin, A., Kennett, B.L.N., Doublier, M.P., Czarnota, K., Fomin, T. and Henson, P., 2020. Moho variations in northern Australia. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.

The magnetotelluric (MT) method is increasingly being applied to mineral exploration under cover with several case studies showing that mineral systems can be imaged from the lower crust to the near surface. Driven by this success, the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) is delivering long-period data on a 0.5° grid across Australia, and derived continental scale resistivity models that are helping to drive investment in mineral exploration in frontier areas. Part of this investment includes higher-resolution broadband MT surveys to enhance resolution of features of interest and improve targeting. To help gain best value for this investment it is important to have an understanding of the ability and limitations of MT to resolve features on different scales. Here we present synthetic modelling of conductive, narrow, near-vertical faults 500 m to 1500 m wide, and show that a station spacing of around 14 km across strike is sufficient to resolve these into the upper crust. However, the vertical extent of these features is not well constrained, with near-vertical planar features commonly resolved as two separate features. This highlights the need for careful interpretation of anomalies in MT inversion. In particular, in an exploration scenario, it is important to consider that a lack of interconnectivity between a lower crustal/upper mantle conductor and conductors higher up in the crust and the surface might be apparent only, and may not reflect reduced mineral prospectivity. Appeared in Exploration Geophysics Journal 05 Dec 2022

The Surface Geology web map service provides two seamless national coverages of Australian bedrock and surficial geology, compiled at 1:1 million scale (displays only at scales less than 1:1500000), and 1:2.5 million scale (displays only at scales greater than 1:1500000). It also contains 1:5 million scale geological regions and metamorphic geology. The service represents outcropping or near-outcropping bedrock units, and unconsolidated or poorly consolidated regolith material covering bedrock.

The 2018 revision of Australia's National Seismic Hazard Assessment (NSHA) represents a substantial improvement from the 2013 NSHA. In particular, this revision will include active fault models, an improved and more homogeneous earthquake catalogue, and greater epistemic uncertainty through a call for third party source models. This paper presents models of seismicity and ground motion that are currently being developed at Geoscience Australia for the NSHA, as implemented in the OpenQuake software. Weighting of logic tree branches for alternative models are discussed, and how these relate to the fundamental datasets on which they are based. For example, a smoothed seismicity model considers only recent seismicity while source models derived from neotectonic data consider a much longer time history. Final weightings will be determined in consultation with members of the Australian seismological community. This abstract was submitted and presented to the 2016 Australian Earthquake Engineering Society Conference (AEES) ( https://aees.org.au/aees-asian-seismological-commission-conferences/)

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.

The Geoscience Australia Structural Measurements Database contains field measurements of geological structure features such as bedding, foliation, lineation, faults and folds from field sites, measured sections, and boreholes. The database is delivered as a layer in Geoscience Australia's "Geological Field Sites, Samples and Observations" web service.

The Surface Geology web map service provides two seamless national coverages of Australian bedrock and surficial geology, compiled at 1:1 million scale (displays only at scales less than 1:1500000), and 1:2.5 million scale (displays only at scales greater than 1:1500000). It also contains 1:5 million scale geological regions and metamorphic geology. The service represents outcropping or near-outcropping bedrock units, and unconsolidated or poorly consolidated regolith material covering bedrock.

<div>This document provides a summary of fault parameterisation decisions made for the faults comprising the fault-source model (FSM) for 2023 National Seismic Hazard Assessment (NSHA23).&nbsp;As with the NSHA18, the FSM for the NSHA23 implementation requires the following parameters: simplified surface trace, dip, dip direction, and slip-rate. As paleoseismic data exist for only a few of the approximately 400 faults within the Australian Neotectonic Features database, we use the Neotectonic Domains model as a framework to parametrise uncharacterised faults.</div>