The Asia-Pacific region experiences some of the world's most violent natural hazards, being exposed to earthquakes, volcanic eruptions, cyclones and monsoons. It is also home to many of the world's most populous megacities with large exposures to hazards. Indeed, government statistics reveal an annual average of 2.7 disasters a day in Indonesia alone. This high risk of natural disasters in developing nations has considerable implications for international aid programs, as disasters significantly compromise the achievement of development goals and the effectiveness of aid investments. Recognising this issue, AusAID requested Geoscience Australia to conduct a broad natural hazard risk assessment of the Asia-Pacific region. This assessment included earthquake, volcanic eruption, tsunami, cyclone, flood, landslide and wildfire hazards. A crucial aspect in the assessment of natural hazard risk is the metric used to define a past disaster and therefore the risk of future disasters. For this preliminary study, we used "significantly impacted population" as the risk metric. This deliberately vague metric is intended to capture the potential for human death, injury, and displacement, as well as prolonged loss of access to essential services and/or shelter, and/or significant damage to agriculture, horticulture and industry such that external assistance is required. However, future work in the Asia-Pacific region will need to be able to determine these vulnerabilities more accurately, considering, for example, the vulnerabilities of buildings and infrastructure in relation to building codes and construction practice, economic cost, and the spatial variability of the intensity of different hazard events. For this study, we determined the frequencies and magnitudes of a range of sudden-onset natural hazards and evaluated the potential disaster impact. Extra emphasis was placed on relatively rare but high impact events that may not be well reflected in the historical record, such as the 2004 Indian Ocean tsunami. We concluded that the potential is high for a natural disaster to seriously affect more than one million people in the Asia-Pacific region, with specific risks as follows: - Megacities in the Himalayan Belt, China, Indonesia and the Philippines are prime candidates for a million-fatality earthquake. - Hundreds of thousands may be seriously affected by volcanic disasters at least once a decade in Indonesia and once every few decades in the Philippines. - The population explosion in the mega-deltas of Asia (e.g., Bangladesh), combined with increasing vulnerability to climate change, indicates that a tsunami, flood or cyclone event significantly impacting tens of millions is likely. - Finally, many Pacific Island nations have a high potential for catastrophic disasters that may significantly impact large proportions of their populations, disasters that are most likely to overwhelm a local and national governments-response and recovery capacity.

The annual cost of sudden onset natural hazards in Australia was estimated in 2001 to be more than 1.1 billion Australian dollars, and the cost of events since then indicates that ongoing efforts are required to manage the risks from bushfires, floods, tropical cyclones, storm surge, severe storms, earthquakes and tsunami in Australia. Tropical Cyclone Larry, which destroyed agricultural crops and property in North Queensland (April 2006), and the Hunter Valley floods (June 2007) are the latest events to each have caused more than a billion dollars of insured and uninsured damage, and they have triggered substantial government relief payments. In 2003 the Council of Australian Governments (COAG) published a review of natural disaster relief and mitigation arrangements in Australia, recommending the development and implementation of a national program of systematic and rigorous disaster risk assessments. The report advocated a `fundamental shift in focus towards cost-effective, evidence-based disaster mitigation. As a result, the Natural Disaster Mitigation Programme (NDMP) was implemented by the Australian Government in collaboration with the State and Territory Governments. The aim of the NDMP was to reduce the costs of natural disasters in Australia, including government disaster relief payments, by supporting risk assessment and mitigation efforts. Geoscience Australia has been engaged as a technical advisor as part of the programme, and has also undertaken a series of national risk assessments for a range of natural hazards. Geoscience Australia has also facilitated the development of a national risk assessment advisory structure and risk assessment framework. Significant progress has been made in developing methods, models and tools for application to impact and risk assessment studies. In this presentation we examine three risk/impact assessment models and associated case studies for earthquake, cyclone/severe wind and tsunami. Each risk/impact model consists of hazard, building and population exposure, and consequence/damage modules. The hazard component considers the probability of occurrence of events of different magnitudes (or categories) and locations, and the propagation of energy from the hazard source to sites of interest. The exposure information is captured in the National Exposure Information System (NEXIS), which captures key attributes of residential and commercial buildings, critical infrastructure, population statistics, and business information. Vulnerability models consider the relationship between hazard parameters (e.g., ground shaking, wind speed, or wave height and speed) and the resulting damage to buildings/infrastructure, and human casualties. Building damage is then linked to repair-cost models that have been developed using quantity survey data. Finally, the costs and repair times are used to evaluate direct and indirect economic impacts at a regional and national scale. Geoscience Australia is making these risk/impact assessment models and information available to the States and Territories and other stakeholders through the release of open source software, interoperable databases, web-based information access, and training of technical experts.

The Joint Australian Tsunami Warning Centre (JATWC) was established in response to the Indian Ocean tsunami in 2004. The JATWC is a collaboration between Geoscince Australia and the Australian Bureau of Meteorology to provide tsunami warnings to the Australian public. This arcticle discusses the actions of the JATWC in response to the magnitude 7.4 earthquake that occurred south of New Zealand on the September 30, 2007. This earthquake generated a tsunami and a potential threat warning was issued for the Australian south east coast. The methods used to analyse the earthquake and the tsunami are examined as well as the future direction of operational capabilities in terms of tsunami modelling.

The Asia-Pacific region experiences some of the world's worst natural hazards, being exposed to frequent earthquakes, volcanic eruptions, cyclones and annual monsoons. It is also home to many of the world's most populous megacities; thus the number of people exposed to hazards in the region is very high. There is abundant evidence showing that the number and seriousness of natural disasters disproportionately affects developing countries more than 90% of natural disaster deaths and 98% of people affected by natural disasters were from developing countries (1991-2005, OFDA/CRED International Disasters Database EM-DAT). Moreover, disasters are increasing in number and size every year due to climate change, rapid population growth and urbanisation. This high risk of natural disasters in developing nations has considerable implications for international aid programs. Natural disasters can significantly compromise development progress and reduce the effectiveness of aid investments. Natural disasters may halt or slow progress towards the achievement of the Millennium Development Goals (MDGs), and in particular, progress on MDG1 "halving poverty and hunger by 2015" may be halted or reversed during a natural disaster. Furthermore during a disaster, aid resources (human and financial) are diverted into humanitarian and emergency response; thus a natural disaster impacts development programs not directly affected by the disaster. Natural hazard risks also influence the type and scale of disaster relief and humanitarian response required by aid agencies. Relatively infrequent, high-magnitude natural disasters, such as the 2004 Indian Ocean tsunami, which are most likely to overwhelm a local and national governments response capacity, are also most likely to require significant humanitarian assistance. An increasing recognition that disasters `erode hard-won development gains and an international policy environment focused on disaster risk reduction (e.g., the Hyogo Framework for Action) has seen the Australian Government, through the Australian Agency for International Development (AusAID), place increased importance on the reduction of natural hazard risk in developing countries. Furthermore, improving our understanding of the frequency, location and magnitude of sudden-onset natural disasters will assist the Australian Government and AusAID plan and prepare for natural disaster response (e.g., through the strategic placement of emergency supplies). Recognising the impact of disasters on development progress, the Australian Government made a decision in 2007 to enhance the humanitarian response, preparedness and capacity of partner governments. In particular, this decision recognised a need for improved natural hazard risk assessments. This strategic approach to disaster risk reduction saw the Natural Hazard Impacts Project at Geoscience Australia conduct a broad hazard risk assessment of the Asia-Pacific region for AusAID in 2007. This assessment included earthquake, volcanic eruption, tsunami, cyclone, flood, landslide and wildfire hazards, with particular attention given to countries considered to be high priority, of interest and of secondary focus to the Australian Government (Figure 1).

This poster shows earthquakes occurring in Australia in 2012 with a background of earthquakes occurring in Australia over the past 10 years. Also included are images produced as part of the analysis of the Ernabella, Moe and Tamworth Earthquakes as well as the yearly summary of earthquake occurrences in Australia.

Indonesia is one of the most disaster prone countries in the world. For 10 years the Australian and Indonesian governments, science agencies and universities, have partnered to strengthen disaster management in Indonesia. Working together on science, technology and policy has greatly improved decision making around disaster management in Indonesia. By helping people prepare for, respond to, and recover from disasters, more lives can be saved, impacts on the most vulnerable members of society reduced, and infrastructure can be protected. Our partnership has concentrated on strengthening the evidence base for formed disaster management by improving: 1) hazard information for earthquake, tsunami, volcano and flood 2) spatial data for exposure (population, building, roads and infrastructure) 3) decision support tool (InaSAFE) to inform disaster response and management decisions. This document outlines the highlights of the Indonesian-Australian collaboration on the use of science and technology in disaster management.

<div>On January 15, 2022, an ongoing eruption at the Hunga volcano generated a large explosion which resulted in a globally observed tsunami and atmospheric pressure wave. This paper presents time series observations of the event from Australia including 503 mean sea level pressure (MSLP) sensors and 111 tide gauges. Data is provided in its original format, which varies between data providers, and a post-processed format with consistent file structure and time-zone. High-pass filtered variants of the data are also provided to facilitate study of the pressure wave and tsunami. For a minority of tide gauges the raw sea level data cannot be provided, due to licence restrictions, but high-pass filtered data is always provided. The data provides an important historical record of the Hunga volcano pressure wave and tsunami in Australia. It will be useful for research in atmospheric and ocean waves associated with large volcanic eruptions. <b>Citation:</b> Davies, G., Wilson, K., Hague, B. et al. Australian atmospheric pressure and sea level data during the 2022 Hunga-Tonga Hunga-Ha’apai volcano tsunami. <i>Sci Data</i> <b>11</b>, 114 (2024). https://doi.org/10.1038/s41597-024-02949-2

This study tests three models for generating stochastic earthquake-tsunami scenarios on subduction zones by comparison with deep ocean observations from 18 tsunamis in 2006-2016. It focusses on the capacity of uncalibrated models to generate a realistic distribution of hypothetical tsunamis, assuming the earthquake location, magnitude and subduction interface geometry are approximately known, while details of the rupture area and slip distribution are unknown. <p>Modelling problems like this arise in tsunami hazard assessment, and when using historical and paleo-tsunami observations to study pre-instrumental earthquakes. Tsunamis show significant variability depending on their parent earthquake's properties, and it is important that this is realistically represented in stochastic tsunami scenarios. To clarify which aspects of earthquake variability should be represented, three scenario generation approaches with increasing complexity are tested: a simple fixed-area-uniform-slip model with earthquake area and slip deterministically related to moment magnitude; a variable-area-uniform-slip model which accounts for earthquake area variability; and a heterogeneous-slip model which accounts for both earthquake area variability and slip heterogeneity. The models are tested using deep-ocean tsunami time-series from 18 events (2006-2016) with moment magnitude $M_{w} > 7.7$. <p>For each model and each observed event a `corresponding family of model scenarios' is generated which includes random scenarios with earthquake location and magnitude similar to the observation, with no additional calibration. For an ideal model (which perfectly characterises the variability of tsunamis) the 18 observed events should appear like a random sample of size 18, created by taking one draw from each of the 18 `corresponding family of model scenarios'. This idea facilitates the development of statistical approaches to test the models. <p>Firstly a goodness-of-fit criterion is developed to identify random scenarios `most similar' to the observed tsunamis, and assess the capacity of different models to produce good-fitting scenarios. Both the heterogeneous-slip and variable-area-uniform-slip models show similar capacity to generate tsunamis similar to observations, while the fixed-area-uniform-slip model performs much more poorly in some cases. Secondly the observed tsunami stage ranges are tested for consistency with the null hypothesis that they were randomly generated by the model. The null hypothesis cannot be rejected for the heterogeneous-slip model, whereas both uniform-slip models exhibit a statistically significant tendency to produce small tsunamis too often. <p>Finally the statistical properties of random earthquake scenarios are compared against those earthquake scenarios that best fit the observations. For the variable-area-uniform-slip models the best-fitting model scenarios have higher slip on average than the random scenarios, highlighting biases in this model. Such biases are not evident in the heterogeneous-slip model. The techniques developed in this study can be applied to test random tsunami scenario generation techniques, identify and partially correct their biases, and provide better justification for their use in applications.

Probabilistic Tsunami Hazard Assessment (PTHA) often proceeds by constructing a suite of hypothetical earthquake scenarios, and modelling their tsunamis and occurrence-rates. Both tsunami and occurrence-rate models are affected by the representation of earthquake slip and rigidity, but the overall importance of these factors for far-field PTHA is unclear. We study the sensitivity of an Australia-wide PTHA to six different far-field earthquake scenario representations, including two rigidity models (constant and depth-varying) combined with three slip models: fixed-area-uniform-slip (with rupture area deterministically related to magnitude); variable-area-uniform-slip; and spatially heterogeneous-slip. Earthquake-tsunami scenarios are tested by comparison with DART-buoy tsunami observations, demonstrating biases in some slip models. Scenario occurrence-rates are modelled using Bayesian techniques to account for uncertainties in seismic coupling, maximum-magnitudes and Gutenberg-Richter b-values. The approach maintains reasonable consistency with the historical earthquake record and spatially variable plate convergence rates for all slip/rigidity model combinations, and facilitates partial correction of model-specific biases (identified via DART-buoy testing). The modelled magnitude exceedance-rates are tested by comparison with rates derived from long-term historical and paleoseismic data and alternative moment-conservation techniques, demonstrating the robustness of our approach. The tsunami hazard offshore of Australia is found to be insensitive to the choice of rigidity model, but significantly affected by the choice of slip model. The fixed-area-uniform-slip model produces lower hazard than the other slip models. Bias adjustment of the variable-area-uniform-slip model produces a strong preference for `compact' scenarios, which compensates for a lack of slip heterogeneity. Thus, both heterogeneous-slip and variable-area-uniform-slip models induce similar far-field tsunami hazard.

Australia's coastline is exposed to tsunamis generated by large subduction earthquakes in the Indian and Pacific Oceans. While recent events had limited impacts in Australia, future earthquakes could in-principle direct much larger waves to our coast. With only a few hours between earthquake detection and tsunami arrival, prior planning is necessary to guide the emergency response. To this end we need an understanding of tsunami hazards: which coastal areas might be inundated, how deep, and how likely? This talk will discuss recent progress in tsunami inundation hazard assessment at Geoscience Australia. We adopt a probabilistic approach to the problem, which involves modelling hypothetical earthquake-tsunamis from major Indian and Pacific Ocean sources, their effects onshore, and their (uncertain) chance of occurrence. To illuminate the science underlying this we will consider: 1. How well tsunami models can simulate historical tsunamis; 2. Representations of hypothetical tsunamis and their natural variability; 3. New techniques to compute onshore hazards while accounting for uncertain earthquake frequencies.