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  • This investigation uses high-resolution optical satellite imagery to quantify vertical surface offsets associated with the intraplate 20 May 2016 Mw 6.0 Petermann Ranges earthquake, Northern Territory, Australia. The ~20 km long NW-trending rupture resulted from reverse motion on a northeast-dipping fault. We measure vertical surface offsets by differencing pre- and post-earthquake digital elevation models (DEMs) derived from in-track stereo Worldview images. This analysis resolves a maximum vertical deformation of 0.8 ? 0.2 m. We validate these results via comparison to field-based observations and interferometric synthetic aperture radar (InSAR). This new method may be particularly useful for remote characterization of earthquake ruptures with larger (>1 m) vertical deformation, where near-rupture InSAR observations are often compromised by decorrelation.

  • 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.

  • 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. Through robust and proven methodologies, technical expertise and trusted data, our national capability can support informed decisions to prepare for and respond to hazard events so that the impact of disasters can be reduced, and to inform where and how our future communities and supporting infrastructure are built.

  • In August 2002 the Council of Australian Governments (COAG) reviewed natural disaster relief and mitigation arrangements for Australia (COAG, 2003). In response to the recommendation to “develop and implement a five-year national program of systematic and rigorous disaster risk assessments”, Geoscience Australia (GA) is undertaking a series of national risk assessments for a range of natural hazards. Fundamental to any risk assessment is an understanding of the exposure including the number and type of buildings, businesses, infrastructure and people exposed to the hazard of interest. Presently there is no nationally consistent exposure database in existence for risk assessment purposes. It is important to emphasise that understanding the risks associated with various hazards requires more detailed information than the population and number of structures at a census district level. The understanding of building type, construction (roof and wall) type, building age, number of storeys, business type and replacement value is critical to understanding the potential impact on Australian communities from various hazards. The National Exposure Information System (NEXIS) is aimed at providing nationally consistent and best available exposure information at the building level. It requires detailed spatial analysis and integration of available demographic, structural and statistical data. Fundamentally, this system is developed from several national spatial datasets as a generic approach with several assumptions made to derive meaningful information. NEXIS underpins scenarios and risk assessments for various hazards. Included are earthquakes, cyclones, severe synoptic wind, tsunami, flood and technogenic critical infrastructure failure. It will be integrated with early warning and alert systems to provide real time assessment of damage or forecast the impact for any plausible hazards. This system is intended to provide a relative assessment of exposure from multiple hazards and provide the geographic distribution of exposure for regional planning. This will be at an aggregated census district level now and at a mesh block level in the future. The system is scoped to capture the residential, business (commercial and industrial), and ancillary (educational, government, community, religious, etc.) infrastructure. Currently the NEXIS architecture is finalised and the system provides residential exposure information. The prototype for business exposure is in progress. The system aims to capture ancillary buildings, infrastructure and various critical infrastructure sector exposures in future. More specific building and socio-economic information will be incorporated as new datasets or sources of information become available. The NEXIS will be able to provide the exposure information for the impact analysis for a region. This database will not support a site specific assessment involving one or two buildings and need more specific information about the particular exposure to estimate the risk at micro level. More detailed information suitable for such analysis will be maintained in reference databases.

  • 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.

  • <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.

  • Four of Australia's largest five population centres are topographically constrained by prominent escarpments (i.e. Sydney, Melbourne, Perth, Adelaide). These escarpments are underlain by faults or fault complexes capable of hosting damaging earthquakes. Paleoseismological investigations over the last decade indicate that the seismogenic character (e.g. recurrence and magnitude) of these structures varies markedly. Uplift rates on range bounding faults in the Mount Lofty Ranges suggest average recurrence times on individual faults for Mmax earthquakes (MW 7.1-7.4) in the order of 10-20 ka. A high density of faults with demonstrated Late Quaternary surface rupture occurring proximally to Adelaide suggests recurrence times for damaging ground shaking at a given location from earthquakes on these faults in the hundreds to low thousands of years. Uplift rates on faults proximal to Melbourne (and the Latrobe Valley, where much of Melbourne's power is generated) in some cases exceed those of the Mount Lofty Ranges. However, a lower relative density of seismogenic faults proximal to the conurbation of Melbourne is suggestive of a lesser hazard than for Adelaide. In contrast to Melbourne and Adelaide, paleoseismological investigations on the Darling Fault near Perth, and the Lapstone Structural Complex near Sydney, indicate average recurrence for Mmax events in the hundreds of thousands to millions of years. Of course, distal larger events and proximal sub-Mmax events have been demonstrated to be damaging in these areas (e.g. 1968 Ms6.8 Meckering, 1989 ML5.6 Newcastle). The same is true for Adelaide and Melbourne (e.g. 1954 ML5.4 Adelaide, 2012 ML 5.4 Moe). Further research is required to demonstrate that earthquakes of sub-morphogenic and morphogenic magnitude might be modelled on the same Guttenberg-Richter distribution curve.

  • 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.

  • Prior to the development of Australian-specific magnitude formulae, the 1935 magnitude corrections by Charles Richter – originally developed for southern California – was almost exclusively used to calculate earthquake magnitudes throughout Australia prior to the 1990s. Due to the difference in ground-motion attenuation between southern California and much of Australia, many historical earthquake magnitudes are likely to be overestimated in the Australian earthquake catalogue. A method has been developed that corrects local magnitudes using the difference between the original (inappropriate) magnitude corrections and the Australian-specific corrections at a distance determined by the nearest recording station likely to have recorded the earthquake. These corrections have reduced the rates of local magnitudes of 4.5 in the historical catalogue by about 30% since 1900, while the number of magnitude 5.0 earthquakes has reduced by about 60% in the same time period. The reduction in the number of moderate-to-large-magnitude earthquakes over the instrumental period yields long-term earthquake rates that are more consistent with present-day rates, since the development of Australian-specific magnitude formulae. The adjustment of historical earthquake magnitudes is important for seismic hazard assessments, which assume a Poisson distribution of earthquakes in space and time.