The aim of the present work is to determine to what extent event-specific tsunami amplitude forecasts from different numerical forecast systems differ, and therefore, how the related products from RTSPs might differ. This is done through comparing tsunami amplitudes for a number of different hypothetical tsunami events within the Indian Ocean, from a number of different tsunami scenario databases.

In response to the Boxing Day tsunami in 2004 the Australian Government funded the creation of the Joint Australian Tsunami Warning Centre (JATWC) to mitigate the tsunami hazard to Australia. Within this system Geoscience Australia is responsible for locating and estimating the magnitude of earthquakes in the Australian region that have the potential to generate a tsunami. On 2 April 2007 a large earthquake (M 8.1) occurred in the Solomon Islands that generated a tsunami and caused severe damage and loss of life in the local area. Geoscience Australia detected the earthquake and issued an earthquake notification which resulted in the JATWC releasing a Tsunami Bulletin for the first time. The tsunami that reached the east Australian coast was small but proved that the systems put in place were effective for warning the Australian public of an approaching tsunami. Geoscience Australia has been developing tools to better characterise the earthquake source. Understanding the type of earthquake and accurately mapping the rupture improves the likelihood of describing the tsunami at the coast. As well as routinely estimating the magnitude Geoscience Australia complements this with estimations of the earthquake fault parameters (W-phase and Centroid Moment Tensor). Modelling of the rupture zone and the tsunami can then follow. This sequence of calculations has been carried out for the Solomon Islands earthquake and explains the tsunami amplitude that was observed on the coast. The modelling shows the earthquake ruptured for 200 km to the northwest with a maximum slip of 5.2 m.

The historical record reveals that at least five tsunamis generated by earthquakes and volcanic eruptions along the Sunda Arc have impacted the West Australian coast (1883, 1977, 1994, 2004 and 2006). We have documented the geomorphic effects of these tsunamis through collation of historical reports, collection of eyewitness accounts, analysis of pre- and post-tsunami satellite imagery and field investigations. These tsunamis had flow depths of less than 3 m, inundation distances of up to several hundred metres and a maximum recorded run-up height of 8 m. Geomorphic effects include off-shore and near-shore erosion and extensive vegetation damage. In some cases, vegetated foredunes were severely depleted or completely removed. Gullies and scour pockets up to 1.5 m deep were eroded into topographic highs during tsunami outflow. Eroded sediments were redeposited as sand sheets several centimetres thick. Isolated coral blocks and rocks with oysters attached (~50 cm A-axis) were deposited over coastal dunes however, boulder ridges were often unaffected by tsunami flow. The extent of inundation from the most recent tsunamis can be distinguished as strandlines of coral rubble and rafted vegetation. It is likely that these features are ephemeral and seasonal coastal processes will obscure all traces of these signatures within years to decades. Recently reported evidence for Holocene palaeotsunamis on the West Australian coast suggests significantly larger run-up and inundation than observed from the historical record. The evidence includes signatures such as chevron dunes that have not been observed from historical events. We have compared the geomorphic effects of historical tsunami with reported palaeotsunami evidence from Coral Bay, the Cape Range Peninsula and Port Samson. We conclude that much of the palaeotsunami evidence can be accounted for via more traditional geomorphic processes such as reef evolution, aeolian dune formation and archaeological site formation.

The Indian Ocean Tsunami of December 26, 2004 made starkly evident the need for better information on tsunami hazard in the Indian Ocean. The tsunami threat faced by Indian Ocean countries consists of a complex mix of tsunami from local, regional and distant sources, whose effects at any particular location in the Indian Ocean are highly dependent on variations in sea floor shape between the source and affected coastlines, complicating tsunami disaster management and the design of tsunami warning systems for the Indian Ocean. In order to provide national governments in the Indian Ocean with the information they need to make informed decisions about tsunami mitigation measures, including development of a warning system, a comprehensive hazard and risk ass In this presentation we discuss the results of this assessment. The study focused on tsunami caused by subduction zone earthquakes, because they are the most frequent source of large tsunami, and tsunami hazard is expressed as annual probability of a tsunami exceeding a given amplitude at a given offshore depth. Because so little is known about the recurrence rates of large megathrust earthquakes in the subduction zones bordering the Indian Ocean, it was decided to develop two hazard maps: a 'low-hazard' end member, based on only those earthquake sources of tsunami for which there is definite evidence, and a 'high-hazard' end member, based on all potential megathrust earthquake sources, including hypothetical ones for which there is no historical or geological evidence, that may affect Indian Ocean coastlines. The actual hazard lies somewhere between these two end members, and the difference between the low hazard and high hazard maps is a simple and effective way to express the uncertainty in the hazard assessment. This uncertainty reflects the lack of knowledge of tsunamigenic earthquake occurrence, and can only be reduced through a better understanding of earthquake and tsunami occurrence in the Indian Ocean.

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.

We have run several thousand tsunami propagation models in order to determine the effect of uncertainty in an earthquake's rupture parameters (specifically strike, dip, rake, depth and magnitude) on the maximum wave height of the tsunami that it creates. We have shown that even for the simple case of a tsunami propagating over flat bathymetry, the Coefficient of Variation (CoV) of the maximum wave height was a complex function of the choice of rupture parameter, distance and azimuth. For example, if the strike of the fault was varied, the CoV was at maximum on either side of the tsunami beam, but if the dip was varied the CoV was at a maximum along the strike of the rupture. We then created maps of the skewness of the distribution of the maximum wave height. They also showed a complex dependence on the choice of the rupture parameter, azimuth and distance. Finally, we have examined the effect of a realistic bathymetry on CoV and skewness by mapping them for three hypothetical earthquakes on different types of subduction zones (Kermadec, Java and the Solomon Islands). These examples showed that the areas of shallow bathymetry in either the local or far field can also make a significant difference to both the CoV and skewness of the distribution of maximum tsunami wave heights at a point.

The Great Sumatra-Andaman Earthquake and Indian Ocean Tsunami of 2004 came as a surprise to most of the earth science community. Few were aware of the potential for the subduction zone off Sumatra to generate giant (Mw>= 8.5) earthquakes, or that such an earthquake might generate a large tsunami. In retrospect, important indicators that such an event might occur appear to have not been well appreciated: (1) the tectonic environment of Sumatra was typical of those in which giant earthquakes occur; (2) GPS campaigns, as well as paleogeodetic studies indicated extensive locking of the interplate contact; (3) giant earthquakes were known to have occurred historically. While it is now widely recognised that the risk of another giant earthquake is high off central Sumatra, just east of the 2004 earthquake, there seems to be relatively little concern about the subduction zone to the north, in the northern Bay of Bengal along the coast of Myanmar. It is shown here that similar indicators suggest the potential for giant earthquake activity is high: (1) the tectonic environment is similar to other subduction zones that experience giant megathrust earthquakes; (2) stress and crustal strain observations indicate the seismogenic zone is locked; and, (3) historical earthquake activity indicates that giant tsunamigenic earthquakes have occurred in the past. These are all consistent with active subduction in the Myanmar subduction zone, and it is hypothesized here that the seismogenic zone there extends beneath the Bengal Fan. The results suggest that giant earthquakes do occur off the coast of Myanmar, and that a very large and vulnerable population is thereby exposed to a significant earthquake and tsunami hazard.

A detailed assessment of the impact of a far-field tsunami on the Australian coastline was carried out in the Steep Point region of Western Australia following the July 17 2006 Java tsunami. Tsunami inundation and run-up were mapped on the basis of eyewitness accounts, debris lines, vegetation damage and the occurrence of recently deposited fish, starfish, corals and sea urchins well above high-tide mark. A topographic survey using kinematic GPS with accuracies of 0.02 metres in the horizontal and 0.04 metres in the vertical recorded flow depths of between 1-2 m, inundation of up to 200 m inland, and a maximum recorded run-up of 7.9 m AHD (Australian Height Datum). The tsunami impacted the sparsely-populated Steep Point coastline close to low tide. It caused widespread erosion in the littoral zone, extensive vegetation damage and destroyed several campsites. Eyewitnesses reported three waves in the tsunami wave train, the second being the largest. A sand sheet, up to 14 cm thick and tapering landwards over 200 m, was deposited over coastal dunes. The deposits are predominantly composed of moderately well sorted, medium grained carbonate sand with some gravel and organic debris. A basal unconformity defines the boundary between tsunami sediments and underlying aeolian dune sand. Evidence for up to three individual waves is preserved as normally graded sequences mantled by layers of dark grey, organic-rich fine silty sand. Given the strong wind regimes in the area, and the similarity of the underlying dune deposits to the tsunami sediments, it is likely that seasonal erosion will remove all traces of these sediment sheets within years to decades.

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).