This report presents three tsunami inundation maps from three potential earthquakes that could threaten the Australia Antarctic Division's station on Macquarie Island. The tsunamis from a magnitude 9.0 earthquake on South America Subduction Zone and from a magnitude 9.0 earthquake Puysegur Subduction Zone caused minimal or strictly coastal inundation to the island. However, the tsunami from a magnitude 8.5 earthquake along the Macquarie Ridge plate margin itself caused substantial inundation across isthmus where the station is located. If this event was to occur, considerable damage to the base could be expected. Given that the Macquarie Ridge plate margin is very seismically active and has a history of large earthquakes, the threat to the station from an event like this is credible. Geoscience Australia recommends that AAD considers taking appropriate tsunami mitigation measures for the base to help reduce the potential impact from this event should it occur.

Using the wind multiplier code (https://pid.geoscience.gov.au/dataset/ga/82481) and an appropriate source of classified terrain data, wind multipliers for all of Queensland at (approximately) 25 metre resolution were created. The wind multipliers have been used to guide impact assessments as part of the Severe Wind Hazard Assessment for Queensland.

Damaging earthquakes in Australia and other regions characterised by low seismicity are considered low probability but high consequence events. Uncertainties in modelling earthquake occurrence rates and ground motions for damaging earthquakes in these regions pose unique challenges to forecasting seismic hazard, including the use of this information as a reliable benchmark to improve seismic safety within our communities. Key challenges for assessing seismic hazards in these regions are explored, including: the completeness and continuity of earthquake catalogues; the identification and characterisation of neotectonic faults; the difficulties in characterising earthquake ground motions; the uncertainties in earthquake source modelling, and the use of modern earthquake hazard information to support the development of future building provisions. Geoscience Australia recently released its 2018 National Seismic Hazard Assessment (NSHA18). Results from the NSHA18 indicate significantly lower seismic hazard across almost all Australian localities at the 1/500 annual exceedance probability level relative to the factors adopted for the current Australian Standard AS1170.4–2007 (R2018). These new hazard estimates have challenged notions of seismic hazard in Australia in terms of the recurrence of damaging ground motions. Consequently, this raises the question of whether current practices in probabilistic seismic hazard analysis (PSHA) deliver the outcomes required to protect communities and infrastructure assets in low-seismicity regions, such as Australia. This manuscript explores a range of measures that could be undertaken to update and modernise the Australian earthquake loading standard, in light of these modern seismic hazard estimates, including the use of alternate ground-motion exceedance probabilities for assigning seismic demands for ordinary-use structures. The estimation of seismic hazard at any location is an uncertain science, particularly in low-seismicity regions. However, as our knowledge of the physical characteristics of earthquakes improve, our estimates of the hazard will converge more closely to the actual – but unknowable – (time independent) hazard. Understanding the uncertainties in the estimation of seismic hazard is also of key importance, and new software and approaches allow hazard modellers to better understand and quantify this uncertainty. It is therefore prudent to regularly update the estimates of the seismic demands in our building codes using the best available evidence-based methods and models.

Tsunamis pose considerable risk to coastal communities around the globe and understanding this risk is a key aspect of emergency management and risk reduction. This paper explores the nature and extent of tsunami hazard to NSW coastal communities and informs tsunami emergency planning and management. We outline the results of recent risk scoping which have examined sources of tsunami hazard, and tsunami history together with results of inundation studies for selected sites and discuss the level of tsunami risk to these NSW communities. We also outline how the results have complimented research by the Australian Bureau of Meteorology in confirming tsunami warning thresholds for NSW. Work undertaken to date indicates the coast of NSW has a moderate tsunami hazard level. Whilst historical impact of tsunami inundation in NSW has been relatively minor, and generally restricted to marine based events, the modelling of selected earthquake generated events indicates the potential for land inundation particularly at high (rare) return periods. Low lying populated communities around estuary foreshores are particularly at risk although results also indicate the potential for inundation of open coast sites at very high (very rare) return periods. The results confirm the need for and support the ongoing collaborative development of emergency management arrangements for tsunami.

Damaging earthquakes in Australia and other regions characterised by low seismicity are considered low probability, high consequence events. Uncertainties in modeling earthquake occurrence rates and ground motions pose unique challenges to forecasting seismic hazard in these regions. In 2018 Geoscience Australia released its National Seismic Hazard Assessment (NSHA18). Results from the NSHA18 indicate significantly lower seismic hazard across almost all Australian localities at the 1/500 annual exceedance probability (AEP) relative to the factors in the Australian earthquake loading standard; the AS1170.4. Due to concerns that the 1/500 AEP hazard factors proposed in the NSHA18 would not assure life safety throughout the continent, the amended AS1170.4 (revised in 2018) retains seismic demands developed in the early 1990s and also introduces a minimum hazard design factor of Z = 0.08 g. The hazard estimates from the NSHA18 have challenged notions of seismic hazard in Australia in terms of the probability of damaging ground motions and raises questions as to whether current practices in probabilistic seismic hazard analysis (PSHA) deliver the outcomes required to protect communities in low-seismicity regions, such as Australia. By contrast, it is also important that the right questions are being asked of hazard modelers in terms of the provision of seismic demand objectives that are fit for purpose. In the United States and Canada, a 1/2475 AEP is used for national hazard maps due to concerns that communities in low-to-moderate seismicity regions are considerably more at risk to extreme ground-motions. The adoption of a 1/2475 AEP seismic demands within the AS1170.4 would bring it in to line with other international building codes in similar tectonic environments and would increase seismic demand factors to levels similar to the 1991 hazard map. This, together with other updates, may be considered for future revisions to the standard. Presented at the Technical Sessions of the 2021 Seismological Society of America Annual Meeting (SSA)

The Mwp 6.1 Petermann Ranges earthquake that occurred on 20 May, 2016 in the Central Ranges, NT, is the largest onshore earthquake to be recorded in Australia since the 1988 Tennant Creek sequence. While geodetic and geophysical analyses have characterized the extent of surface rupture and faulting mechanism respectively, a comprehensive aftershock characterization has yet to be performed. Data has been acquired from a 12-station temporary seismic network deployed jointly by the ANU and Geoscience Australia (GA), collected from five days following the mainshock to early October. Taking advantage of enhanced automatic detection techniques using the SeisComP3 real-time earthquake monitoring software within the National Earthquake Alerts Centre (NEAC) at GA, we have developed a comprehensive earthquake catalogue for this mainshock-aftershock sequence. Utilising the NonLinLoc location algorithm combined with a Tennant Creek-derived velocity model, we have preliminarily located over 5,800 aftershocks. With additional spatio-temporal analyses and event relocation, our objective will be to use these aftershocks to help delineate the geometry of the headwall rupture along the Woodroffe Thrust. These high-resolution aftershock detection techniques are intended to be implemented in real-time within the NEAC following future significant Australian intraplate earthquakes. This paper was presented at the Australian Earthquake Engineering Society 2021 Virtual Conference, Nov 25 – 26.

In 2009 Geoscience Australia (GA), Australia's national geoscience agency, initiated a project to update the National Earthquake Hazard Map for Australia. This talk will summarise the work done by the Earthquake Hazard Section to update the National Earthquake Hazard Maps and will also present the new maps themselves. The maps have mainly been designed to be used as a basis informing Australia's earthquake loading code. However they can also be used to help to improve Australia's ability to better prepare for earthquakes more generally. This talk will provide a brief overview of the work done for this project. Topics to be highlighted in this talk include how we put together a new catalogue of earthquakes for Australia and revised their magnitudes. Our new method for automatically classifying earthquakes as main shocks, foreshocks and aftershocks will also be discussed, as well the new set of earthquake source zones we have produced. In addition, the talk will also discuss new way we have tried to estimate the maximum expected magnitude for earthquakes in Australia from the results of GA's neotectonics program. The completely new set ground motion prediction equations for eastern Australia we have produced will also be presented. Finally, the talk will also show the revised and updated set of earthquake hazard maps based on the latest version of GA's EQRM (Earthquake Risk Model) code. The hazard and spectral curves for selected locations around Australia will be shown and the potential implications for earthquake risk will be briefly discussed. From the 9th International CO2 conference, Beijing 2013

Modern geodetic and seismic monitoring tools are enabling the study of moderate-sized earthquake sequences in unprecedented detail. Discrepancies are apparent between the surface deformation envelopes ‘detectable’ using these tools, and ‘visible’ to traditional ground-based methods of observation. As an example, we compare the detectible and visible surface deformation caused by a sequence of earthquakes near Lake Muir in southwest Western Australia in 2018. A shallow MW 5.3 earthquake on the 16th of September 2018 was followed on the 8th of November 2018 by a MW 5.2 event in the same region. Focal mechanisms for the events suggest reverse and strike-slip rupture, respectively. Interferometric Synthetic Aperture Radar (InSAR) analysis of the events suggests that the ruptures are in part spatially coincident and deformed the Earth’s surface over ~ 12 km in an east-west direction and ~ 8 km in a north-south direction. Field mapping, guided by the InSAR results, reveals that the first event produced an approximately 3 km long and up to 0.5 m high west-facing surface rupture, consistent with slip on a moderately east-dipping fault. No surface deformation unique to the second event was identifiable on the ground. New rupture length versus magnitude scaling relationships developed for non-extended cratonic regions as part of this study allow for the distinction between ‘visible’ surface rupture lengths (VSRL) from field-mapping and ‘detectable’ surface rupture lengths (DSRL) from remote sensing techniques such as InSAR, and suggest longer ruptures for a given magnitude than implied by commonly used scaling relationships.

Tropical cyclone return period wind hazard layers developed using the Tropical Cyclone Risk Model. The hazard layers are derived from a catalogue of synthetic tropical cyclone events representing 10000 years of activity. Annual maxima are evaluated from the catalogue and used to fit a generalised extreme value distribution at each grid point.

Modelling tropical cyclone Yasi using TCRM