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.

It's hard to believe eight years has passed since the Great East Japan Earthquake occurred that devastated so much of Japan. In November, I was very fortunate to participate in a United National International Strategy for Disaster Reduction meeting in Sendai, which included two days of site visits to areas hit by the tsunami.

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.

To follow

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 effect of offshore coral reefs on the impact from a tsunami remains controversial. For example, field surveys after the 2004 Indian Ocean tsunami indicate that the energy of the tsunami was reduced by natural coral reef barriers in Sri Lanka, but there was no indication that coral reefs off Banda Aceh, Indonesia had any effect on the tsunami. In this paper, we investigate whether the Great Barrier Reef offshore Queensland, Australia, may have weakened the tsunami impact from the 2007 Solomon Islands earthquake. The fault slip distribution of the 2007 Solomon Islands earthquake was firstly obtained by teleseismic inversion. The tsunami was then propagated to shallow water just offshore the coast by solving the linear shallow water equations using a staggered grid finite difference method. We used a relatively high resolution (approximately 250m) bathymetric grid for the region just off the coast containing the reef. The tsunami waveforms recorded at tide gauge stations along the Australian coast were then compared to the results from the tsunami simulation when using both the realistic 250m resolution bathymetry and with two grids with an imaginary bathymetry. One of the grids with an imaginary bathymetry removes the coral reef and interpolates an artificial bathymetry across it. The other imaginary grid replaces the reef with a flat plane at a depth equal to the mean water depth of the Great Barrier Reef. From the comparison between the synthetic waveforms both with and without the Great Barrier Reef, we found that the Great Barrier Reef significantly weakened the tsunami impact. According to our model, the coral reefs delayed the tsunami arrival time by 5-10 minutes, decreased the amplitude of the first tsunami pulse to half or less, and made the period of the tsunami longer.

The tragic events of the 2004 Indian Ocean Tsunami highlighted the real threat posed by tsunamis to coastal communities worldwide. With subduction zones to the north and east of Australia, tsunamis pose a real threat to the Australian coast. Geoscience Australia has been developing methodologies for quantifying the severity of tsunami impacts to assist emergency management authorities in planning for this threat. Tsunami inundation modelling is computationally intensive and is often restricted to a small number of discrete communities. As a result, communities must be prioritised for this detailed modelling. One method for prioritisation is the Probabilistic Tsunami Hazard Assessment (PTHA) of Australia. In the PTHA, tsunamis were modelled from all likely earthquake sources across the deep ocean using a computationally faster linear solution and coarser model domain. Results are considered valid only to the 100 m depth contour, where we calculate return periods for tsunami wave height around Australia and generate a database of tsunami wave forms. However, tsunami waves are shaped considerably by the bathymetry between the 100 m depth contour and the coast, and tsunami behaviour near the coast is therefore highly non-linear, dependent on elevation, coastline shape, wave height, period and momentum. This non-linear reality of the near shore environment raises a number of questions. Is offshore wave height alone the best predictor of onshore tsunami hazard? Analytical solutions to the 1-D shallow water equations exist for predicting wave run-up on plane beaches. Can these be applied to offshore waves to measure inundation potential? Or are other metrics, such as wave energy, more appropriate? Comparisons with results from detailed inundation models will explore the utility of these measures for prioritising communitie

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.

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.

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.