The tragic events of the Indian Ocean tsunami on 26 December 2004 highlighted shortcomings in the alert and response systems for tsunami threats to Western Australia's (WA) coastal communities. To improve community awareness and understanding of tsunami hazard and potential impact for Western Australia, the Fire and Emergency Services Authority of WA (FESA) established a collaborative partnership with GA in which science and emergency management expertise was applied to identified communities.

Diatom assemblages in sandy deposits of the 2004 tsunami at Phra Thong Island, Thailand may provide clues to flow conditions during the tsunami. The tsunami deposits contain one or more beds that fine upward, commonly from medium sand to silty very fine sand. Diatom assemblages of the lowermost portion of the deposit predominantly comprise of unbroken beach and subtidal species that live attached to sand grains. The dominant taxa shift to marine plankton species in the middle of the bed and to a mix of freshwater, brackish, and marine species near the top. These trends are consistent with expected changes in current velocities of tsunami through time. During high current velocities, medium sand is deposited; only beach and subtidal benthic diatoms attached to sediment can be incorporated into the tsunami deposit. High shear velocity keeps finer material, including planktonic diatoms in suspension. With decreasing current velocities, finer material including marine plankton can be deposited. Finally, during the lull between tsunami waves, the entrained freshwater, brackish, and marine species settle out with mud and plant trash. Low numbers of broken diatoms in the lower medium sand implies rapid entrainment and deposition, whilst selective breakage of marine plankton (Thalassionema nitzschioides, and Thalassiosira and Coscinodiscus spp.) in the middle portion of the deposit probably results from abrasion in the turbulent current before deposition.

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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 quality and type of elevation data used in tsunami inundation models can lead to large variations in the estimated inundation extent and tsunami flow depths and speeds. In order to give confidence to those who use inundation maps, such as emergency managers and spatial planners, standards and guidelines need to be developed and adhered to. However, at present there are no guidelines for the use of different elevation data types in inundation modelling. One reason for this is that there are many types of elevation data that differ in vertical accuracy, spatial resolution, availability and expense; however the differences in output from inundation models using different elevation data types in different environments are largely unknown. This study involved simulating tsunami inundation scenarios for three sites in Indonesia, of which the results for one of these, Padang, is reported here. Models were simulated using several different remotely-sensed elevation data types, including LiDAR, IFSAR, ASTER and SRTM. Model outputs were compared for each data type, including inundation extent, maximum inundation depth and maximum flow speed, as well as computational run-times. While in some cases, inundation extents do not differ greatly, maximum depths can vary substantially, which can lead to vastly different estimates of impact and loss. The results of this study will be critical in informing tsunami scientists and emergency managers of the acceptable resolution and accuracy of elevation data for inundation modelling and subsequently, the development of elevation data standards for inundation modelling in Indonesia.

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.

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.

The Mw=7.8 earthquake of 15 July, 2009 occurred along a section of the subduction zone south of New Zealand, where the Puysegur Block subducts beneath the Pacific Plate. The orientation of this subduction zone suggests that tsunamis generated along it pose a significant threat to the southeast coast of Australia, but since it had not experienced megathrust rupture until the 15 July event, the question of whether it was accumulating strain energy whose release could result in a large tsunami was open. We have used seismic, tsunami, geodetic and SAR data to study this earthquake and find that it involved primarily thrust motion on a fault plane dipping east at a shallow angle, consistent with expectations for a megathrust earthquake. The ability to use multiple data types to study this earthquake lead to improved ability to resolve parameters such as rupture velocity that are often difficult to constrain with seismic data alone. Seismic array data agree with rupture modelling of broadband waveforms in their prediction of a bilateral component to the earthquake rupture. Also, a tsunami of about 10 cm peak-to-peak amplitude was recorded by two tsunameter buoys in the Tasman Sea west of the epicenter, and we find that the tsunami travel times indicated by these data suggest the earthquake was characterised by a low rupture velocity of around 1 km/s. We will also present comparisons against GPS and InSAR data that further constrain parameters of the rupture. Finally, we will discuss the potential for earthquake activity further south along the Puysegur Trench, which poses a tsunami threat particularly to the eastern coast of Tasmania.

On 17 July 1998, a magnitude 7.0 earthquake rocked the north coast region of Papua New Guinea (PNG). The Aitape tsunami took over 2000 lives, caused extensive damage to houses and public infrastructure, and altered the environment around the village.