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  • The Natural Hazard Impacts Project (NHIP) at Geoscience Australia has developed modelling techniques that enable coastal inundation to be predicted during a tsunami. A Collaborative Research Agreement between Geoscience Australia and the Fire and Emergency Services Authority (FESA) was formed in 2005 to understand tsunami risk and inform emergency management in WA. Through this partnership a significant tsunami risk was identified in NW Western Australia, leading to the development of inundation models for several coastal communities in this region, including Onslow and Exmouth. Recognising the importance of this research to Geoscience Australia, FESA and the communities of Onslow and Exmouth, this year's graduate project was designed to assist the NHIP and to further strengthen ties with FESA and community organisations. The project had several distinct outcomes which can be divided into data acquisition and community interaction. High quality elevation data was gathered by GPS surveying in order to ascertain the quality of the Digital Elevation Model (DEM) that is currently used in inundation models. Improved accuracy in the elevation data allows the capture of subtle changes in topography that may not be present in the existing DEM and so may improve model accuracy. Secondly, ground-truthing of predicted inundation areas supplements the survey data, provides critical assistance in the production of accurate inundation models and potentially aids in the production of emergency plans. Prior to fieldwork a community-specific tsunami awareness brochure was designed and produced for Onslow. This brochure was presented to Onslow local emergency managers and FESA personnel, and subsequently to Emergency Management Australia and the Bureau of Meteorology. It has received widespread positive feedback, and consequently may provide a template for other community brochures in similarly vulnerable regions of Australia. Finally, graduates represented Geoscience Australia at several community meetings in Onslow where NHIP research was presented. These meetings provided insight into specific community concerns in the event of a tsunami and provided an opportunity for the attendees to ask questions about tsunamis and their impacts. Fortuitously this community interaction also led to the discovery of anecdotal evidence of past tsunami events in Onslow, including the tsunami triggered by the 1883 Krakatau eruption, a 1937 tsunami that may be attributed to an earthquake near Java, and the 1994 and 2004 tsunamis.

  • As part of its response to the Indian Ocean tsunami of 26 December 2004, the Australian Government funded the establishment of the Australian Tsunami Warning System (ATWS). The ATWS has three objectives: (i) provide a comprehensive warning system for Australia, (ii) contribute to international efforts to establish an Indian Ocean Tsunami Warning System, and (iii) facilitate tsunami warnings in the Pacific Ocean. The ATWS has been issuing warnings for Australia since July 2006, and in 2007 started sharing advisories with other warning centres. It expects to begin issuing advisories directly to other countries during 2009. To be successful, an end-to-end warning system must develop mitigation strategies to prepare communities for tsunami. Mitigation strategies include taking steps to minimise the impact of a tsunami, eg., avoiding building in the likely inundation zone and building sea walls when this can't be avoided, and response procedures, such as evacuations, when an event occurs. The warning system must monitor for tsunami and issue warnings; and it must implement response strategies when a tsunami approaches the coastline and a recovery phase afterwards (Figure 1). In Australia, responsibility for these phases is shared by Commonwealth, State/Territory and Local Governments. Etc ...

  • The major tsunami disaster in the Indian Ocean in 2004, and the subsequent large events off the south coast of Indonesia and in the Solomon Islands, have dramatically raised awareness of the possibility of potentially damaging tsunamis in the Australian region. Since the 2004 Indian Ocean Tsunami (IOT), a number of emergency management agencies have worked with Geoscience Australia to help to develop an understanding of the tsunami hazard faced by their jurisdictions. Here I will discuss both the major tsunamis over the last few years in the region and the recent efforts of Geoscience Australia and others to try to estimate the likelihood of such events in the future. Since 2004, a range of probabilistic and scenario based hazard assessments have been completed through collaborative projects between Geoscience Australia and other agencies in Australia and the region. These collaborations have resulted in some of the first ever probabilistic tsunami hazard assessments to be completed for Australia and for a wide range of other countries in the southwest Pacific and Indian Oceans. These assessments not only estimate the amplitude of a tsunami that could reach the coast but also its probability. The assessments allow crucial questions from emergency managers (such as 'Just how often do large tsunamis reach our coasts?) to be quantitatively addressed. In addition, they also provide a mechanism to prioritise communities for more detailed risk assessments. This work allows emergency managers to base their decisions on the best available science and data for their jurisdiction instead of relying solely on intuition.

  • Real-time Earthquake Monitoring at the Joint Australian Tsunami Warning Centre From November 2006, Geoscience Australia began to monitor, analyse and alert for potentially tsunamigenic earthquakes that could threaten Australia's coastline, on a 24/7 basis. This ongoing role forms part of the Australian Tsunami Warning System (ATWS) that was announced in the Australian Government's May 2005 budget to complement the Indian Ocean Tsunami Warningand Mitigation System that was being implemented by the International Oceanographic Commission. The Joint Australian Tsunami Warning Centre (JATWC), as the operational arm of the ATWS, became fully operational in October 2008. It combines the efforts of Geoscience Australia's seismic measurement and analysis and the Australian Bureau of Meteorology's coastal and deep ocean sea level monitoring and modelling to produce timely tsunami warnings for Australia and the Indian Ocean region. A beneficiary of the setup of the JATWC was Geoscience Australia's ongoing role of reporting local Australian earthquakes, as it is now also able to function on a 24/7 basis; an upgrade to its earlier on-call arrangement. This paper describes the setup of Australia's tsunami warning capability and the methodology, systems and processes used to publish potentially tsunamigenic, local Australian and large international earthquake information. The paper will also highlight some of the future development activities to improve the accuracy and timeliness of Geoscience Australia's earthquake information.

  • The development of the Indian Ocean Tsunami Warning and mitigation System (IOTWS) has occurred rapidly over the past 5 or so years. One of the major elements of the IOTWS is the concept of a Regional Tsunami Watch Provider (RTWP). An RTWP is a centre that provides an advisory tsunami forecast service to one or more National Tsunami Warning Centres (NTWC). One requirement of an RTWP is that they must have access to numerical model-based tsunami forecasts. Products provided to the NTWCs are also exchanged with other RTWPs. An important part of the RTWP concept is that the services provided by the RTWPs are inter-operable. In this context, 'inter-operable' means that the products exchanged are in the same format and relate to the same physical parameters. The aim of the present work is to determine to what extent event-specific tsunami amplitude forecasts from different numerical forecast systems might differ, and therefore, how the related products from RTWPs might differ.

  • As the Australian plate slowly pushes under the Eurasian plate, massive stresses build up in the crust. These stresses also cause the Eurasian plate to be slowly forced upwards - part of the process that builds the mountains and volcanoes of Indonesia, as well as creating the many earthquakes felt in that region of the world each year. When the stresses get too great, the plates will suddenly slip causing massive movements in the seafloor. The part of the crust nearest to the fault zone rapidly moves upwards by a metre or so, lifting the entire body of water above it. A hundred kilometres away the opposite may happen: the seafloor drops and the ocean above it also falls. These two movements (the sudden rise and fall of the seafloor hundreds of kilometres apart), combine to cause a series of tsunami waves which move away from the line of the fault in both directions.

  • Landslides can happen on the seafloor, just like on land. Areas of the seafloor that are steep and loaded with sediment are more prone to undersea landslides, such as the edge of the continental slope. When an undersea landslide occurs (perhaps after a nearby earthquake) a large mass of sand, mud and gravel can move down the slope. This movement will draw the water down and may cause a tsunami that will travel across the ocean.

  • As the tsunami moves across the open ocean it is almost undetectable on the ocean surface. In this example, the tsunami waves are only about half a metre high but have a wavelength of 200 kilometres. Travelling at speeds of up to eight or nine hundred kilometres an hour (the speed of a commercial passenger jet), it will take each wave about 15 minutes to pass a slow moving ship.

  • As the tsunami leaves the deep water of the open ocean and approaches the shallower waters near the coast, it slows down and may grow in height depending on the shape of the seafloor. A tsunami that is unnoticeable by ships at sea may grow to be several metres or more in height near the coast. Our example tsunami is now 1.5 metres high with a wavelength of 100 kilometres and is moving at about 400 kilometres an hour.

  • Along the Aceh-Andaman subduction zone, there was no historical precedent for an event the size of the 2004 Sumatra-Andaman tsunami; therefore, neither the countries affected by the tsunami nor their neighbours were adequately prepared for the disaster. By studying the geological signatures of past tsunamis, the record may be extended by thousands of years, leading to a better understanding of tsunami frequency and magnitude. Sedimentary evidence for the 2004 Sumatra-Andaman tsunami and three predecessor great Holocene tsunamis is preserved on a beach ridge plain on Phra Thong Island, Thailand. Optically stimulated luminescence ages were obtained from tsunami-laid sediment sheets and surrounding morphostratigraphic units. Single-grain results from the 2004 sediment sheet show sizable proportions of near-zero grains, suggesting that the majority of sediment was well-bleached prior to tsunami entrainment or that the sediment was bleached during transport. However, a minimum-age model needed to be applied in order to obtain a near-zero luminescence age for the 2004 tsunami deposit as residual ages were found in a small population of grains. This demonstrates the importance of considering partial bleaching in water-transported sediments. The OSL results from the predecessor tsunami deposits and underlying tidal flat sands show good agreement with paired radiocarbon ages and constrain the average recurrence of large late Holocene tsunami on the western Thai coast to between 500 to 1000 years. This is the first large-scale application of luminescence dating to gain recurrence estimates for large Indian Ocean tsunami. These results increase confidence in the use of OSL to date tsunami-laid sediments, providing an additional tool to tsunami geologists when material for radiocarbon dating is unavailable. Through an understanding of the frequency of past tsunami, OSL dating of tsunami deposits can improve our understanding of tsunami hazard and provide a means of assessing fu