Results from an audit of 32 petroleum exploration wells in the Bass Basin have shown that approximately half of the wells in the basin were invalid tests due to off-structure drilling or mis-interpretation. Of the remaining wells, primary reasons for failure were lack of effective seal, timing, trap validity, lack of access to mature source rocks or reservoir problems. In parts of the basin the regional seal (Demons Bluff Shale) has undergone a period of structural inversion during the late Tertiary resulting in seal breach. Anticlinal closures of Eocene age were particularly affected, while structures located on fault-bounded basement highs were less affected, and provide the only fields within the basin. In the Yolla and White Ibis fields, access to mature source rocks was provided by large-displacement, non-sealing faults, that linked the upper EVG reservoirs with deeper source rocks. Traps without this conduit have as yet been unsuccessful. Sandy units within the Eastern View Group in the Pelican Trough are tight reservoirs that have good porosity but poor permeability. This is due to diagenetic effects that prohibited the creation of secondary porosity and permeability. Although identified risks within the basin can be minimised, the key to successful exploration will be finding traps that were in-place prior to the generation of hydrocarbons, but did not undergo significant Tertiary inversion.

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.

INFORMING NATURAL HAZARD RISK MITIGATION THROUGH A RELIABLE DEFINITION OF EXPOSURE Krishna Nadimpalli, Mark Edwards, Mark Dunford Risk & Impact Analysis Group, Geoscience Australia GPO Box 378, Canberra, ACT 2601, Australia, krishna.nadimpalli@ga.gov.au Fundamental to any risk assessment is an understanding of the infrastructure and people exposed to the hazard under consideration. In Australia there is presently no nationally consistent exposure database that can provide this information. The need to better understand risk was recognised in the report on natural disaster relief and mitigation arrangements made to the Council of Australian Governments (COAG) in 2003. The report included a recommendation to develop and implement a five-year national program of systematic and rigorous disaster risk assessments. In response to this Geoscience Australia (GA) is undertaking a series of national risk assessments for a range of natural hazards. This work is being underpinned by a parallel development of a national definition of community exposure called the National Exposure Information System (NEXIS). The NEXIS aims to provide nationally consistent and best available exposure information at the building level. The building types considered are residential, business (commercial and industrial), and ancillary (educational, government, community, religious, etc.). NEXIS requires detailed spatial analysis and integration of available demographic, structural and statistical data. Fundamentally, this system is being developed from several national spatial datasets as a generic approach with several assumptions made to derive meaningful information. NEXIS is underpinning scenarios and risk assessments for various hazards. Included are earthquakes, cyclones, severe synoptic wind, tsunami, flood and technogenic critical infrastructure failure. The NEXIS architecture is completed and the system currently provides residential exposure information nationally. The prototype for business exposure is well developed and a national definition of business exposure will be generated by June 2008. Ancillary buildings and various critical infrastructure sector exposures will be incorporated into the future. While the present approach is largely generic, more specific building and socio-economic information will be incorporated as new datasets or sources of information become available. Opportunities also exist for NEXIS to be integrated with early warning and alert systems to provide real time assessments of damage or to forecast the impact for a range of hazards. This paper describes the methodologies used by NEXIS and how these will be advanced in the future to provide a more complete and specific definition of exposure to inform severe hazard risk assessment, risk mitigation and post event response.

Geographical information systems (GIS) have been used to model building flood damage in South East Queensland. The research shows that if a flood with a 1% annual exceedence probability (AEP) occurred simultaneously in all rivers in the region, 47 000 properties would be inundated, with about half of the properties likely to experience overfloor flooding. 90% of affected properties are located in the Brisbane-Bremer River system and the Gold Coast catchment. 89% of properties affected by flooding are residential. Nearly 60% of the residential flood damage is located in the Brisbane-Bremer River system, with damage estimated to be highest in those areas which historically have suffered high flood losses. Equivalent average damage per residential building is highest in the Gold Coast catchment. If the cost of the actual damages were to be spread among all residential buildings in South East Queensland, than the equivalent flood damage would be 1.09% damage from a flood with a 1% AEP.

The report presents a framework for assessng in quantitative terms the cost of the weather related hazards of severe wind, flood inundation, storm surge, bushfire and hail. It has been developed with reference to the risk assessment approaches used by the insurance and catastrophic loss modelling industry. For each hazard the specific data inputs to each component of the impacts framework are summarised as a list of implementation needs. Finally, the report identifies areas where impact models are immature or not readily available in the public domain.

The National Exposure Information System (NEXIS) is a capability developed by Geoscience Australia, an agency within the portfolio of the federal Department of Resources, Energy and Tourism. NEXIS is a nationally consistent database of building assets, essential infrastructure, economic activity and demographic information. All these community elements are at risk to natural hazards and will be exposed to the unavoidable, long term influences of climate change. The system collects and collates a broad range of information for research and policy development in Australia, including that associated with climate change adaptation. The development of NEXIS has been undertaken in parallel to ongoing national assessments of climate change risk for hazards such as storm surge, severe wind, bushfire and extreme temperature NEXIS employs a largely statistical approach to developing a national definition of exposure using a number of existing databases maintained by others. These include the Geocoded National Address File (GNAF), the Property Cadastre, the Business Registry, and census datasets from the Australian Bureau of Statistics. Costing modules developed by quantity surveyors have also been incorporated to provide estimates of building replacement costs across Australia. State Government departments have supplied data on local building information in Tasmania and South Australia. The Census of Land Use and Employment (CLUE) has also been made available by local government for comprehensive information about land use, employment and economic activity across the entire Greater Melbourne area.

Following the tragic events of the Indian Ocean tsunami on 26 December 2004 it became obvious there were shortcomings in the response and alert systems for the threat of tsunami to Western Australia's (WA) coastal communities. The relative risk of a tsunami event to the towns, remote indigenous communities, and infrastructure for the oil, gas and mining industries was not clearly understood in 2004. Consequently, no current detailed response plans for a tsunami event in WA coastal areas existed. The Boxing Day event affected the WA coastline from Bremer Bay on the south coast, to areas north of Exmouth on the north-west coast, with a number of people requiring rescue from abnormally strong currents and rips. There were also reports of personal belongings at some beaches inundated by wave activity. More than 30 cm of water flowed down a coast-side road in Geraldton on the mid-west coast, and Geordie Bay at Rottnest Island (19 km of the coast of Fremantle) experienced five 'tides' in three hours, resulting in boats hitting the ocean bed a number of times. The vivid images of the devastation caused by the 2004 event across a wide geographical area changed the perception of tsunami and achieved an appreciation of the potential enormity of impact from this low frequency but high consequence natural hazard. With WA's proximity to the Sunda Arc, which is widely recognised as a high probability area for intra-plate earthquakes, the need to develop a better understanding of tsunami risk and model the potential social and economic impacts on communities and critical infrastructure along the Western Australian coast, became a high priority. Under WA's emergency management arrangements, the Fire and Emergency Services Authority (FESA) has responsibility for ensuring effective emergency management is in place for tsunami events across the PPRR framework.

The impacts of climate change, including sea level rise and the increased frequency of storm surge events, will adversely affect infrastructure in a significant number of Australian coastal communities. In order to quantify this risk, Geoscience Australia in collaboration with the Department of Climate Change and Energy Efficiency, have undertaken a first-pass national assessment which has identified the extent and value of infrastructure that are potentially vulnerable to impacts of climate change. We have utilised the best available national scale information to assess the vulnerability of Australia's coastal zone to the impacts of climate change. In addition to assessing coastal vulnerability assuming the current population, we also examined the changes in exposure under a range of future population scenarios provided by the Australian Bureau of Statistics. Continuation of the current trend for significant development in the coastal zone increases the number and value of residential buildings potentially vulnerable by 2100. We found that over 270,000 residential buildings are potentially vulnerable to the combined impacts of inundation and recession by 2100. This equates to a replacement value of approximately AUD$72 billion. Nearly 250,000 residential buildings were found to be potentially vulnerable to inundation only, which equates to AUD$64 billion. Queensland and New South Wales have the largest vulnerability (considering both value and number of buildings affected). Nationally, approximately 33,000 km of road and 1,500 km of rail infrastructure are potentially at risk by 2100. These results are influencing policy and adaptation planning decisions made by federal, state and local government.

The cyclonic wind hazard over the Australian region is determined using synthetic tropical cyclone event sets derived from general circulation models (GCMs). Cyclonic wind hazard is influenced by the frequency, intensity and spatial distribution of tropical cyclones, all of which may change under future climate regimes due to influences such as warmer sea surface temperatures and changes in the global circulation. Cyclonic wind hazard is evaluated using a statistical-parametric model of tropical cyclones - the Tropical Cyclone Risk Model (TCRM) - which can be used to simulate many thousands of years of cyclone activity. TCRM is used to generate synthetic tracks which are statistically similar to the input event set - be it an historical record of other synthetic event set. After applying a parametric wind field to the simulated tracks, we use the aggregated wind fields to evaluate the average recurrence interval wind speeds for three IPCC AR4 scenarios, and make comparisons to the corresponding average recurrence interval wind speed estimates for current climate simulations. Results from the analysis of two GCMs are presented.

This report is a major risk assessment project based on metropolitan Perth, the capital city of Western Australia. Completed in June 2005, the report is the final publication in Geoscience Australia's Cities Project. Approximately 72% of Western Australia's population of around 1.3 million live in the Perth metropolitan area. Significant areas of Perth are situated along the banks of the flood prone Swan River and close to Australia's most active earthquake zone. There are several limestone belts to the north and south of Perth where karst systems have been discovered and the city's coastline suffers from coastal erosion as a result of high winds and fierce storms. The study aimed at estimating the impact on the Perth community of several sudden-onset natural hazards. The natural hazards considered are both meteorological and terrestrial in origin. The hazards investigated most comprehensively are riverine floods in the Swan and Canning Rivers, severe winds in metropolitan Perth, and earthquakes in the Perth region. Some socioeconomic factors affecting the capacity of the citizens of Perth to recover from natural disaster events have been analysed and the WA data compared with data from other Australian states. Additionally, new estimates of earthquake hazard have been made in a zone of radius around 200km from Perth, extending east into the central Wheatbelt. The susceptibility of the southwest WA coastline to sea level rise from climate change has also been investigated. A commentary on the tsunami risk to WA coastline communities is also included. A postage and handling fee will be associated with the distribution of this product.