<p>The mechanisms that lead to the localisation of stable continental region (SCR) seismicity, and strain more generally, remain poorly understood. Recent work has emphasised correlations between the historical record of earthquake epicentres and lateral changes in the thickness, composition and/or viscosity (thermal state) of the lithospheric mantle, as inferred from seismic velocity/attenuation constraints. Fluid flow and the distribution of heat production within the crust have also been cited as controls on the location of contemporary seismicity. The plate margin-centric hypothesis that the loading rate of crustal faults can been understood in terms of the strain rate of the underlying lithospheric mantle has been challenged in that a space-geodetic strain signal is yet to be measured in many SCRs. Alternatives involving the release of elastic energy from a pre-stressed lithosphere have been proposed. <p>The Australian SCR crust preserves a rich but largely unexplored record of seismogenic crustal deformation spanning a time period much greater than that provided by the historical record of seismicity. Variations in the distribution, cumulative displacement, and recurrence characteristics of neotectonic faults provide important constraint for models of strain localisation mechanisms within SCR crust, with global application. This paper presents two endmember case studies that illustrate the variation in deformation characteristics encountered within Australian SCR crust, and which demonstrate the range and nature of the constraint that might be imposed on models describing crustal deformation and seismic hazard.

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.

A new finite volume algorithm to solve the two dimensional shallow water equations on an unstructured triangular mesh has been implemented in the open source ANUGA software, jointly developed by the Australian National University and Geoscience Australia. The algorithm allows for 'discontinuous-elevation', or 'jumps' in the bed profile between neighbouring cells. This has a number of benefits compared with previously implemented 'continuous-elevation' approaches. Firstly it can preserve stationary states at wet-dry fronts, while also permitting simulation of very shallow frictionally dominated flow down slopes as occurs in direct-rainfall flood models. Additionally the use of discontinuous-elevation enables the sharp resolution of rapid changes in the topography associated with e.g. narrow rectangular drainage channels, or buildings, without the computational expense of a very fine mesh. The approach also supports a simple and computationally efficient treatment of river walls. A number of benchmark tests are presented illustrating these features of the algorithm, along with its application to urban flood hazard simulation and comparison with field data.

The disasters caused by tsunamis the last 10 years have highlighted the need for a thorough understanding of the global and regional tsunami hazard and risk. At present, the 2004 and 2011 tsunamis hint that their induced risk are dominated by large infrequent events with possibly long return periods. However, an in-depth understanding of how individual contributions from sources of different strength and frequency govern the hazard and risk is presently not clear. A first global analysis of tsunami hazard using earthquake sources was conducted in 2008 on behalf of the UN-ISDR Global Assessment Report (GAR). Recently, this initiative has resulted in the first, fully probabilistic global tsunami hazard assessment. Economic loss calculations based on building fragility curves largely derived from recent major tsunamis have also been included to assess the risk. Still, this complex assessment is premature. Further efforts are needed, requiring joint expertise covering a wide range of topics such as the understanding of sources, hydrodynamics, probability and statistics, as well as vulnerability and exposure. Therefore, there is a dire need for a joint interdisciplinary effort delivering data and tools that may help decision makers in assessing their tsunami hazard and risk. To this end, we propose to establish a Global Tsunami Model (GTM) that will emphasize tsunami hazard and risk analysis on a global scale. The GTM will be based on the initial work in GAR, but should eventually involve a broader community. The motivation, the needs, and the possible contributors for such a GTM will be discussed.

Geoscience Australia provides 24/7 monitoring of seismic activity within Australia and the surrounding region through the National Earthquake Alerts Centre (NEAC). Recent enhancements to the earthquakes@GA web portal now allow users to view felt reports, submitted online – together with reports from other nearby respondents – using the new interactive mapping feature. Using an updated questionnaire based on the US Geological Survey’s Did You Feel It? System, Geoscience Australia now calculate Community Internet Intensities (CIIs) to support near-real-time situational awareness applications. Part of the duty seismologists’ situational awareness and decision support toolkit will be the production of real-time “ShakeMaps.” ShakeMap is a system that provides near-real-time maps of shaking intensity following significant earthquakes. The software ingests online intensity observations and spatially distributed instrumental ground-motions in near-real-time. These data are then interpolated with theoretical predictions to provide a grid of ground shaking for different intensity measure types. Combining these predictions with CIIs provides a powerful tool for rapidly evaluating the likely impact of an earthquake. This paper describes the application of the new felt reporting system and explores its utility for near-real-time ShakeMaps and the provision of situational awareness for significant Australian earthquakes.

The 2018 National Seismic Hazard Assessment of Australia incorporated 19 alternative seismic-source models. The diversity of these models demonstrates the deep epistemic uncertainty that exists with regards to how best to characterize intraplate seismicity. A complex logic tree was developed to incorporate the alternative models into a single hazard model. Similarly, a diverse range of ground-motion models were proposed for use and incorporated using a logic tree. Expert opinion was drawn upon to weight the alternative logic tree branches through a structured expert elicitation process. This process aims to transparently and reproducibly characterize the community distribution of expert estimates for unknown parameters and thereby quantify the epistemic uncertainty around estimates of seismic hazard in Australia. We achieve a multi-model rational consensus where each model, and each expert, is, in accordance with the Australian cultural myth of egalitarianism, given a ‘fair go’. Yet despite this process, we find that the results are not universally accepted. A key issue is a contested boundary between what is scientifically reducible and what remains epistemologically uncertain, with a particular focus on the earthquake catalog. Furthermore, a reduction, on average, of 72% for the 10% in 50 years probability of exceedance peak ground acceleration levels compared with those underpinning existing building design standards, challenges the choice of metrics upon which design codes are based. As questions of epistemic uncertainty are quantified or resolved, changes in our understanding of how the hazard behaves should inform dialogue between scientists, engineers and policy makers, and a re-appraisal of the metrics used to inform risk management decisions of societal importance.

The Australian Flood Risk Information Portal (the portal) is an initiative of the Australian Government, established following the devastating floods across Eastern Australia in 2011. The portal is a key component of the National Flood Risk Information Project (NFRIP), and aims to provide a single point of access to Australian flood information. Currently much of Australia's existing flood information is dispersed across disparate sources, making it difficult to find and access. The portal will host data and tools that allow public discovery, visualisation and retrieval of flood studies, flood maps, satellite derived water observations and other related information, all from a single location. The portal will host standards and guidelines for use by jurisdictions and information custodians to encourage best practice in the development of new flood risk information. While the portal will initially host existing flood information, the architecture has been designed to allow the portal content to grow over time to meet the needs of users. The aim is for the portal to display data for a range of scenarios from small to extreme events, though this will be dependent on stakeholder contributions. Geoscience Australia's Australian Flood Studies Database is the portal's data store of flood study information. The database includes metadata created through a purpose-built data entry application, and over time, information harvested from state-operated catalogues. For each entry the portal provides a summary of the flood study, including information on how the study was done, what data was used, what flood maps were produced and for what scenarios, as well as details on the custodian and originating author. If the study included an assessment of damage, details such as estimates of annual average damage, or the number of properties affected during a flood of a particular likelihood will also be included. During the last phase of development downloadable flood study reports and their associated flood maps have been added to the portal where available. As the portal is populated it will increasingly host mapped flood data, or link to flood data and maps held in authoritative databases hosted by State and Territory bodies. Mapping data to be made accessible through the portal will include flood extents and to a lesser degree information on water depths. The portal will also include water observations obtained from Geoscience Australia's historic archive of Landsat imagery. This data will show whether a particular location was 'wet' at some point during the past 30 years. While this imagery does not necessarily represent the peak of a flood or show water depth, the data will support the validation and verification process of hydrologic and hydraulic flood modelling. This work will prove useful particularly in rural areas where there is little or no flood information. The portal also provides flood information custodians with the ability to either upload mapped data directly to the portal or to make this data accessible via web services. Data management tools and standards, developed through NFRIP, will enable data custodians to map their data to agreed standards for delivery through the portal. A portal framework and supporting principles has been developed to guide the maintenance and development of the portal.

The Flood Study Summary Services support discovery and retrieval of flood hazard information. The services return metadata and data for flood studies and flood inundation maps held in the 'Australian Flood Studies Database'. The same information is available through a user interface at http://www.ga.gov.au/flood-study-web/. A 'flood study' is a comprehensive technical investigation of flood behaviour. It defines the nature and extent flood hazard across the floodplain by providing information on the extent, level and velocity of floodwaters and on the distribution of flood flows. Flood studies are typically commissioned by government, and conducted by experts from specialist engineering firms or government agencies. Key outputs from flood studies include detailed reports, and maps showing inundation, depth, velocity and hazard for events of various likelihoods. The services are deliverables fom the National Flood Risk Information Project. The main aim of the project is to make flood risk information accessible from a central location. Geoscience Australia will facilitate this through the development of the National Flood Risk Information Portal. Over the four years the project will launch a new phase of the portal prior to the commencement of each annual disaster season. Each phase will increase the amount of flood risk information that is publicly accessible and increase stakeholder capability in the production and use of flood risk information. flood-study-search returns summary layers and links to rich metadata about flood maps and the studies that produced them. flood-study-map returns layers for individual flood inundation maps. Typically a single layer shows the flood inundation for a particular likelihood or historical event in a flood study area. To retrieve flood inundation maps from these services, we recommend: 1. querying flood-study-search to obtain flood inundation map URIs, then 2. using the flood inundation map URIs to retrieve maps separately from flood-study-map. The ownership of each flood study remains with the commissioning organisation and/or author as indicated with each study, and users of the database should refer to the reports themselves to determine any constraints in their usage.

In the last few years there have been several probabilistic seismic hazard assessments (PSHA) of Adelaide. The resulting 500 year PGA obtained are 0.059, 0.067, 0.109 and 0.141. The differences between the first three are readily accounted for by choice of GMPE, how faults are included and differences in recurrence estimation, with each of these having a similar level of importance. As no GMPEs exist for the Mt Lofty and Flingers Ranges the choices of GMPEs were all based on geological analogies. The choice of at what weighting to include low attenuation, that is a stable continental crust, GMPE was most important. At a return period of 500 year the inclusion of faults was not necessarily significant. The choice of whether the faults behaved with Characteristic or Gutenberg-Richter recurrence statistics had the highest impact on the hazard with the choice of slip rate the next most important. A low slip rate Characteristic fault, while increasing the hazard for longer return periods (i.e. ~2500 years), results in only a minor increase at 500 years. The magnitude frequency distribution b-value for the four studies were 1.043, 0.88, 0.915 and 0.724. For the same activity in the magnitude range of 3.0 to 3.5, the activity level at M 6.0 is an order of magnitude higher for a b-value of 0.724 compared to a b-value of 1.043. This increase in activity rate of larger earthquakes significantly increases the hazard. The average of the first three studies is 0.078±0.022 (0.056 -0.100) g. This range is reflecting the intrinsic uncertainty in calculating PSHAs where many of the inputs are poorly constrained. The results for the highest hazard level PSHA study (i.e. 0.141g) can be explained by their use of a low b-value (i.e. 0.724). M. Leonard1, R. Hoult2, P. Somerville3, G. Gibson2, D. Sandiford2, H. Goldsworthy2, E. Lumantarna2 and S Spiliopoulos1. 1Geoscience Australia, 2The University of Melbourne, 3 URS

The Tropical Cyclone Impact Map provides guidance on areas likely to be impacted by severe winds due to tropical cyclones. The impact zones are generated by Geoscience Australia's Tropical Cyclone Risk Model (TCRM), and are based on the tropical cyclone forecast information published by the Bureau of Meteorology's Tropical Cyclone Warning Centres. TCRM applies a 2-dimensional parametric wind field to the forecast track provided by the Bureau of Meteorology, and translates the wind speeds into an indicator of potential damage to housing. Uncertainty in the forecast track is not included in the product.