This paper reports efforts to improve the knowledge of the vulnerability to riverine inundation of domestic housing types found in the Brisbane Ipswich area of Queensland. Riverine inundation is inundation by slowing rising river water where the water velocity is sufficiently low as not to cause velocity-related damage. Generic housing types are derived from surveyed exposure and analytical vulnerability relationships are developed from assessments of repair works at different inundation depths and compared to the results of a postal survey of dwellings affected by flooding in January, 2011.

A selection of images and short animations explaining key aspects of the 2004 Indian Ocean/ Sumatra tsunami, revised and issued for release to the media and other interested organisations on the tenth anniversary of the disaster. This selection updates existing resources previously released by Geoscience Australia.

Internal advice on tsunami, earthquake and severe wind hazards for the Kimbe Bay region, derived from large-scale hazard assessments. This advice (refer TRIM D2021-55557) was provided to the Australia Pacific Climate Partnership (APCP) as part of Geoscience Australia's (GA's) contributions to the program. (In confidence report to APCP, not for distribution)

Internal advice on tsunami, earthquake and severe wind hazards for the Vanimo Port region, derived from large-scale hazard assessments. This advice (refer TRIM D2021-52746) was provided to the Australia Pacific Climate Partnership (APCP) as part of Geoscience Australia's (GA's) contributions to the program. (In confidence report to APCP, not for distribution)

Tsunami hazard maps are generated for the Mentawai Islands, West Sumatra, Indonesia, to support evacuation and disaster response planning. A random heterogeneous slip generator is used to forward model a suite of earthquake rupture scenarios on the Mentawai Segment of the Sunda Subduction Zone. A total of 1000 rupture models that fit constraints provided by coral and geodetic records of coseismic vertical deformation from great earthquakes in 1797, 1833 and 2007 are used to model inundation and define a maximum inundation zone that envelopes all of these scenarios. Results are compared with single scenario hazard assessments developed by experts and agreed through scientific consensus building processes to assess the additional value of modelling a suite of scenarios to obtain a more robust estimate of potential inundated areas by incorporating uncertainty in the earthquake source. The model presented here, like all tsunami hazard assessments, is based on assumptions about the characteristics of future events based on past events, however by sampling a range of plausible outcomes we gain a more robust estimate of which areas may be inundated during a tsunami within the bounds of our assumptions.

Geoscience Australia is currently drafting a new Australian Earthquake Hazard Map (or more correctly a series of maps) using modern methods and models. Among other applications, the map is a key component of Australia’s earthquake loading code AS1170.4. In this paper we provide a brief history of national earthquake hazard models in Australia, with a focus on the map used in AS1170.4, and provide an overview of the proposed changes for the new maps. The revision takes advantage of significant improvements in both the data sets and models used for earthquake hazard assessment in Australia since the original map was produced. These include:  Earthquake observations up to and including 2010  Improved methods of declustering earthquake catalogues and calculating earthquake recurrence  Ground-motion prediction equations (i.e. attenuation equations) based on response spectral acceleration rather than peak ground velocity, peak ground acceleration or intensity-based relations.  Revised earthquake source zones  Improved maximum magnitude earthquake estimates based on palaeoseismology  The use of open source software for undertaking probabilistic seismic hazard assessment which promotes testability and repeatability The following papers in this series will address in more detail the changes to the earthquake catalogue, earthquake recurrence and ground motion prediction equations proposed for use in the draft map. The draft hazard maps themselves are presented in the final paper.

An updated National Seismic Hazard Assessment of Australia was released in 2018 (the NSHA18). This assessment leveraged off advances in earthquake-hazard science in Australia and analogue tectonic regions to offer many improvements over its predecessors. The outcomes of the assessment represent a significant shift in the way national-scale seismic hazard is modelled in Australia, and so challenged long-held notions of seismic hazard amongst the Australian seismological and earthquake engineering community. The NSHA18 is one of the most complex national-scale seismic hazard assessments conducted to date, comprising 19 independent seismic source models (contributed by Geoscience Australia and third-party contributors) with three tectonic region types, each represented by at least six ground motion models each. The NSHA18 applied a classical probabilistic seismic hazard analysis (PSHA) using a weighted logic tree approach, where the model weights were determined through two structured expert elicitation workshops. The response from the participants of these workshops was overwhelmingly positive and the participants appreciated the opportunity to contribute towards the model’s development. Since the model’s publication, Geoscience Australia has been able to reflect on the choices made both through the expert elicitation process and through decisions made by the NSHA18 team. The consequences of those choices on the production of the final seismic hazard model may not have been fully appreciated prior to embarking on the development of the NSHA18, nor during the expert elicitation workshops. The development of the NSHA18 revealed several philosophical challenges in terms of characterising seismic hazard in regions of low seismicity such as Australia. Chief among these are: 1) the inclusion of neotectonic faults, whose rupture characteristics are underexplored and poorly understood; 2) processes for the adjustment and conversion of historical earthquake magnitudes to be consistently expressed in terms of moment magnitude; 3) the relative weighting of different seismic-source classes (i.e., background, regional, smoothed seismicity, etc) for different regions of interest and exceedance probabilities; 4) the assignment of Gutenberg-Richter b-values for most seismic source models based on b-values determined from broad neotectonic domains, and; 5) the characterisation and assignment of ground-motion models used for different tectonic regimes. This paper discusses lessons learned through the development of the NSHA18, identifies successes in the expert elicitation and modelling processes, and explores some of the abovementioned challenges that could be reviewed for future editions of the model. Abstract presented at the 17th World Conference on Earthquake Engineering (17WCEE )

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.

Seismic hazard models, commonly produced through probabilistic seismic hazard analysis, are used to establish earthquake loading requirements for the built environment. However, there is considerable uncertainty in developing seismic hazard models, which require assumptions on seismicity rates and ground-motion models (GMMs) based on the best evidence available to hazard analysts. This paper explores several area-based tests of long-term seismic hazard forecasts for the Australian continent. ShakeMaps are calculated for all earthquakes of MW 4.25 and greater within approximately 200 km of the Australian coastline using the observed seismicity in the past 50 years (1970-2019). A “composite ShakeMap” is generated that extracts the maximum peak ground acceleration “observed” in this 50-year period for any site within the continent. The fractional exceedance area of this composite map is compared with four generations of Australian seismic hazard maps for a 10% probability of exceedance in 50 years (~1/500 annual exceedance probability) developed since 1990. In general, all these seismic hazard models appear to be conservative relative to the observed ground motions that are estimated to have occurred in the last 50 years. To explore aspects of possible prejudice in this study, the variability in ground-motion exceedance was explored using the Next Generation Attenuation-East GMMs developed for the central and eastern United States. The sensitivity of these results is also tested with the interjection of a rare scenario earthquake with an expected regional recurrence of approximately 5,000 - 10,000 years. While these analyses do not provide a robust assessment of the performance of the candidate seismic hazard for any given location, they do provide—to the first order—a guide to the performance of the respective maps at a continental scale. This paper was presented at the Australian Earthquake Engineering Society 2021 Virtual Conference, Nov 25 – 26.

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.