Type of resources
Codes for the statistical analysis of storm wave clustering.
<p>Geoscience Australia has 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, coupled with larger kp factors, have challenged notions of seismic hazard in Australia in terms of the recurrence of damaging ground motions. As a consequence, the new hazard estimates have raised questions over the appropriateness of the prescribed probability level used in the AS1170.4 to determine appropriate seismic demands for the design of ordinary-use structures. Therefore, it is suggested that the ground-motion exceedance probability used in the current AS1170.4 be reviewed in light of the recent hazard assessment and the expected performance of modern buildings for rarer ground motions. <p>Whilst adjusting the AS1170.4 exceedance probability level would be a major departure from previous earthquake loading standards, it would bring it into line with other international building codes in similar tectonic environments. Additionally, it would offer opportunities to further modernise how seismic demands are considered in Australian building design. In particular, the authors highlight the following additional opportunities: 1) the use of uniform hazard spectra to replace and simplify the spectral shape factors, which do not deliver uniform hazard across all natural periods; 2) updated site amplification factors to ensure continuity with modern ground-motion models, and; 3) the potential to define design ground motions in terms of uniform collapse risk rather than uniform hazard. Estimation of seismic hazard at any location is an uncertain science. However, as our knowledge improves, our estimates of the hazard will converge on the actual – but unknowable – (time independent) hazard. 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.
<p>Critical infrastructure systems provide essential services central to the functioning of Australian communities and the economy. Research into historic catastrophic failures of infrastructure suggests two factors have the strongest influence on such failures: system complexity and tight coupling within such systems. While complexity of these lifeline systems is recognised, the latter factor is often not well-understood, especially in the context of severe natural hazards. <p>Proposed in this paper is a methodology to study the performance of lifeline infrastructure under hazard impact, where key component parameters of complex lifeline systems, along with component interactions, are integrated within an executable model. This model can then be subjected to any number of virtual hazards to assist in identification of non-obvious failure mechanisms, quantify post-hazard system performance, and conduct experimentation with alternate mitigation measures. <p>This process allows for investigating the combined effect of various parameters including component fragilities, system topology, restoration times and costs with their uncertainties, redundancies, and the expected hazard. Much of this information is commercially sensitive or only accessible to specialist groups. Ensuring access to, and effective combination of, such information requires a trusted information-sharing collaboration framework between cross-sectoral experts. This collaboration requires participation from infrastructure operators, researchers, engineers, and government entities. This paper outlines a methodology and tools that have been utilised within such a collaborative project, and documents key learnings from the effort, along with observations on improvement strategies.
The HazImp system enables users to analyse the impact of natural hazards. HazImp is capable of assessing the impact of a range of hazards including, but not limited to, floods and tropical cyclones. HazImp uses a set of pre-processed inputs, perform logic based analysis using predefined models and produce a range of quantitative outputs. These inputs may be produced by existing external systems including hazard modelling applications. HazImp outputs may include aggregated values, statistical figures, diagrams and spatial maps to describe the impact of the natural hazard to the study area. HazImp assesses the impact of a natural hazard as a combination of three fundamental elements: • Hazard - the type of hazard and its properties; • Exposure - elements that are or could be subject to the hazard; • Vulnerability – an element’s physical or social susceptibility to the hazard. All three elements are required to properly assess the impact of a hazard and a change in any element will affect the impact results. HazImp supports a set of inputs, each corresponding to one of these three elements. HazImp is designed to support a wide variety of scenarios making it highly customisable to the event or events being analysed. In particular, HazImp is compatible with existing GA systems. HazImp supports two primary business cases for natural hazard impact assessment. The first, to support risk assessment and mitigation where system response times can be generous and could be as long as weeks. The second, is forecasting the impact of an imminent event, where an assessment is needed in real-time.
Benfield and Geoscience Australia intend to collaborate to improve their respective understanding of risks from natural hazards in Australia. The aim of this project is to exchange ideas, data and models in order to support the respective groups risk modeling expertise.
As part of the 2018 National Seismic Hazard Assessment (NSHA), we compiled the geographic information system (GIS) dataset to enable end-users to view and interrogate the NSHA18 outputs on a spatially enabled platform. It is intended to ensure the NSHA18 outputs are openly available, discoverable and accessible to both internal and external users. This geospatial product is derived from the dataset generated through the development of the NSHA18 and contains uniform probability hazard maps for a 10% and 2% chance of exceedance in 50 years. These maps are calculated for peak ground acceleration (PGA) and a range of response spectral periods, Sa(T), for T = 0.1, 0.2, 0.3, 0.5, 1.0, 2.0 and 4.0 s. Additionally, hazard curves for each ground-motion intensity measure as well as uniform hazard spectra at the nominated exceedance probabilities are calculated for key localities.