tsunami
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This poster shows earthquakes occurring in Australia in 2012 with a background of earthquakes occurring in Australia over the past 10 years. Also included are images produced as part of the analysis of the Ernabella, Moe and Tamworth Earthquakes as well as the yearly summary of earthquake occurrences in Australia.
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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.
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The major tsunamis of the last few years have dramatically raised awareness of the possibility of potentially damaging tsunami reaching the shores of Australia and to the other countries in the region. Here we present three probabilistic hazard assessments for tsunami generated by megathrust earthquakes in the Indian, Pacific and southern Atlantic Oceans. One of the assessments was done for Australia, one covered the island nations in the Southwest Pacific and one was for all the countries surrounding the Indian Ocean Basin
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Colour brochure about tsunami awareness and what to do in case of a tsunami threat. This pamphlet is produced jointly by Emergency Management Australia, Geoscience Australia and the Bureau of Meteorology.
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Keynote presentation to cover * the background to tsunami modelling in Australia * what the modelling showed * why the modelling is important to emergency managers * the importance of partnerships * future challenges
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The aim of this document is to provide the Fire and Emergency Services Authority of Western Australia (FESA WA) with a preliminary assessment of tsunami impact to Mandurah. This follows preliminary assessments to six South West (SW) Western Australian (WA) communities previously modelled (Carnarvon, Geraldton, Fremantle, Rockingham, Bunbury and Busselton) to underpin evidence-based tsunami planning and preparation activities. This also follows the preliminary assessment of tsunami impact for six North West Shelf (NW Shelf) communities that used deep water tsunami hazard information from the probabilistic tsunami hazard assessment for WA. This hazard assessment has now been updated and completed at a national level. The current impact assessment draws tsunami hazard information from the more recent national tsunami hazard assessment that describes the probability of a given tsunami wave amplitude at the 100 m contour being exceeded.
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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.
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Earthquakes represent an increasing threat to Oceania because of increasing concentration of populations in built environments that are vulnerable either to ground shaking or to landslides or tsunamis generated by earthquakes. The estimated impact of earthquake shaking is strongly dependent on details of the earthquake rupture such as stress drop, depth and rupture extent. For example, the magnitude 7.5 South Sumatra earthquake, 60 km from the city of Padang (30/09/09), killed over 1100 people, while the much larger South Sumatra earthquakes of magnitude 8.4 and 7.9 (12/09/07), only 130 km from Bengkulu and 190 km from Padang, respectively, collectively killed only 12 people. Similarly the ability of earthquakes to generate tsunamis that impact coastal populations is strongly influenced by the updip extent of fault rupture and its orientation with respect to population centres: the tsunami generated by the magnitude 8.1 Samoa earthquake (29/09/09) killed over 180 people, while that generated by the magnitude 7.8 Vanuatu earthquake (7/10/09) killed no one. Our ability to forecast the potential impacts of future earthquakes on a population centre is therefore dependent not only on our knowledge of the occurrence probability for an event of a certain magnitude, but also on our understanding of the different styles of rupture that may occur. Rapid estimate of impact, for purposes such as tsunami early warning or early assessment of post-disaster response requirements, is dependent on our abilit to rapidly and reliably estimate not only magnitude and epicentre, but also details of earthquake rupture.
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The Asia-Pacific region experiences some of the world's most violent natural hazards, being exposed to earthquakes, volcanic eruptions, cyclones and monsoons. It is also home to many of the world's most populous megacities with large exposures to hazards. Indeed, government statistics reveal an annual average of 2.7 disasters a day in Indonesia alone. This high risk of natural disasters in developing nations has considerable implications for international aid programs, as disasters significantly compromise the achievement of development goals and the effectiveness of aid investments. Recognising this issue, AusAID requested Geoscience Australia to conduct a broad natural hazard risk assessment of the Asia-Pacific region. This assessment included earthquake, volcanic eruption, tsunami, cyclone, flood, landslide and wildfire hazards. A crucial aspect in the assessment of natural hazard risk is the metric used to define a past disaster and therefore the risk of future disasters. For this preliminary study, we used "significantly impacted population" as the risk metric. This deliberately vague metric is intended to capture the potential for human death, injury, and displacement, as well as prolonged loss of access to essential services and/or shelter, and/or significant damage to agriculture, horticulture and industry such that external assistance is required. However, future work in the Asia-Pacific region will need to be able to determine these vulnerabilities more accurately, considering, for example, the vulnerabilities of buildings and infrastructure in relation to building codes and construction practice, economic cost, and the spatial variability of the intensity of different hazard events. For this study, we determined the frequencies and magnitudes of a range of sudden-onset natural hazards and evaluated the potential disaster impact. Extra emphasis was placed on relatively rare but high impact events that may not be well reflected in the historical record, such as the 2004 Indian Ocean tsunami. We concluded that the potential is high for a natural disaster to seriously affect more than one million people in the Asia-Pacific region, with specific risks as follows: - Megacities in the Himalayan Belt, China, Indonesia and the Philippines are prime candidates for a million-fatality earthquake. - Hundreds of thousands may be seriously affected by volcanic disasters at least once a decade in Indonesia and once every few decades in the Philippines. - The population explosion in the mega-deltas of Asia (e.g., Bangladesh), combined with increasing vulnerability to climate change, indicates that a tsunami, flood or cyclone event significantly impacting tens of millions is likely. - Finally, many Pacific Island nations have a high potential for catastrophic disasters that may significantly impact large proportions of their populations, disasters that are most likely to overwhelm a local and national governments-response and recovery capacity.
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Palaeotsunami investigations can enhance our understanding of tsunami hazard in the Australian region, providing a means of assessing future risk. Previous researchers have suggested that at least six large tsunami impacted the NSW coast during the Holocene, some with run-up in excess of +100 m asl and inundation of 10 km inland. However, this evidence is contentious as it focuses on poorly understood rocky shoreline features and proposes tsunami signatures that have not been described in other parts of the world. If such evidence is substantiated, it has profound implications for the tsunami preparedness of the NSW communities. This study focuses on late Holocene coastal sedimentary records from backshore environments in NSW to develop an assessment of whether catastrophic marine inundation such as tsunami played a significant role in coastal evolution. The advantages of studying backshore environments are that a more continuous sedimentary record is likely to be preserved than on rocky shorelines and an estimate of tsunami recurrence can be obtained if several tsunamigenic units are found in sequence. Fifty cores from sixteen coastal water bodies in southern and central NSW were studied for evidence of past tsunami inundation. Potentially tsunamigenic sediment horizons were identified in some water bodies, which may be a result of localised submarine slump-induced palaeotsunami. However the small size and discontinuous distribution of these sedimentary units does not support the theory of "mega-tsunami" inundation. If such "mega-tsunami" had occurred, definitive evidence for them should be preserved on a wider scale in the backshore sedimentary record. This suggests that previous research for mega-tsunami on the NSW coastline needs to be re-evaluated.