Acehtsunami

Natural hazards impact on every Australian State and Territory. These hazards include bushfires, cyclones, earthquakes, floods, landslides, severe weather, tsunami, and volcanoes. The phenomena threaten lives and damage private and public assets as well as disrupt water, power, transport, and communication services. These hazards and their associated impacts also can seriously affect employment and incomes to industry, agriculture, commerce and public administration.

In Australia, natural hazards are estimated to cost an average of A$1.25 billion annually (BTE, 2001), but the cost of individual hazards can be much greater. For example, in 1989 an earthquake cost the community in the New South Wales city of Newcastle an estimated A$4.5 billion.Natural hazards cannot be averted, but their consequences can be minimised by implementing mitigation strategies and reducing the potential impact to areas which are most vulnerable.As part of its extensive work on natural hazard risk research, Geoscience Australia monitors and assesses earth-surface processes which pose a risk to Australia. It gathers data and develops tools for use by governments and other authorities to help them make Australia as safe as possible from natural hazards.

Earthquakes and tsunamis might continue to threaten residents living along the country’s coastal areas with experts warning that the two disasters are going through a cycle this year.Tsunami researcher Rahman Hidayat of the Coastal Dynamic Analysis Body at the Agency for the Assessment and Application of Technology (BPPT) said earthquake-triggered tsunamis were going through a cycle this year.He pointed to Sumatra’s west coast, especially Mentawai Islands regency, as the location which requires the most attention.The west coast of Sumatra, he said, has two earthquake-prone zones, which have entered a 200-240 year cycle; the last cycle of earthquakes and tsunamis occurred there between 1797 and 1833.In the past five years, he said his office and the Southern California University had worked together with world research institutions to give the quake-prone areas more attention.

They also jointly conducted research on possible major earthquakes, the epicenters of which, they predicted, are likely to be on Sumatra’s west coast.”"It turned out the quake that struck Bengkulu was located only some 200 kilometers north of the location we predicted,”" he said.He also warned residents living in other regions, such as Banggai in South Sulawesi — a region which also has a history marked by massive earthquakes and tsunamis — and areas from Pacitan to Banyuwangi in East Java.”"The threat is serious and might be more dangerous (than previous disasters). This year (could be) the time when Indonesia experiences more earthquakes and tsunamis,”" Rahman said.He said another tsunami researcher, Lorry Dongler of Humbold University in the U.S., has also raised similar concerns about the earthquake and tsunami cycle in the country.

On May 22, 1960, at 19:11 GMT, an earthquake occurred off the coast of South Central Chile. A Pacific-wide tsunami was triggered by the earthquake, which had a surface-wave magnitude of 8.6, an epicenter of 39.5° S, 74.5° W, and a focal depth of 33 km. The number of fatalities associated with both the tsunami and the earthquake has been estimated to be between 490 to 2,290. Damage cost estimates were over a half billion dollars.

Aerial view of coastal area on Isla Chiloe, Chile, showing tsunami damage and wave extent. Two hundred deaths were reported here from the tsunami generated just off Chile’s coast by the magnitude 8.6 earthquake. The inhabitants, fearing the earthquake, took to small boats to escape the shaking. The trough of the tsunami arrived just 10 to 15 minutes after the earthquake, along more than 500 m of the coast. Upon the return of the sea in a thunderous breaker, all boats were lost. The most serious effects occurred in an area extending from Concepcion on the Chilean coast to the south end of Isla Chiloe. Photograph Credit: Unknown. Source: National Geophysical Data Center.

Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the earth’s crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. Waves are formed as the displaced water mass, which acts under the influence of gravity, attempts to regain its equilibrium. When large areas of the sea floor elevate or subside, a tsunami can be created.

Large vertical movements of the earth’s crust can occur at plate boundaries. Plates interact along these boundaries called faults. Around the margins of the Pacific Ocean, for example, denser oceanic plates slip under continental plates in a process known as subduction. Subduction earthquakes are particularly effective in generating tsunamis.

Published 15 January 2005 As survivors along the coasts devastated by the tsunami on 26 December 2004 start to clear the debris, the world’s attention is turning to how these communities are going to rebuild their towns and villages. When the unthinkable happens again, will they be any better prepared? ‘When you think of the hundreds of millions of dollars that have been lined up, there is a real chance that we simply rebuild the risky circumstances that we had before,’ warns Reid Basher of the UN’s International Strategy for Disaster Reduction (ISDR) in Bonn, Germany. ‘This is often the case in earthquake situations. The rebuilding reinstates the risk in the big rush to get everything going again.’

But rebuilding also gives communities an opportunity to prepare for future tsunamis, and at little extra cost. The nations that border the Pacific, which are in most danger from earthquake-triggered waves, have pioneered ways to protect themselves. ‘Tsunami defence work consists of political, social, economic, cultural and engineering matters. Not one of them can be neglected,’ says Nobuo Shuto, a tsunami engineer at Iwate Prefectural University in Iwate, Japan.

PASADENA, Calif. – A wave of new NASA research on tsunamis has yielded an innovative method to improve existing tsunami warning systems, and a potentially groundbreaking new theory on the source of the December 2004 Indian Ocean tsunami.In one study, published last fall in Geophysical Research Letters, researcher Y. Tony Song of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., demonstrated that real-time data from NASA’s network of global positioning system (GPS) stations can detect ground motions preceding tsunamis and reliably estimate a tsunami’s destructive potential within minutes, well before it reaches coastal areas.

The method could lead to development of more reliable global tsunami warning systems, saving lives and reducing false alarms.Conventional tsunami warning systems rely on estimates of an earthquake’s magnitude to determine whether a large tsunami will be generated. Earthquake magnitude is not always a reliable indicator of tsunami potential, however. The 2004 Indian Ocean quake generated a huge tsunami,while the 2005 Nias (Indonesia) quake did not, even though both had almost the same magnitude from initial estimates. Between 2005 and 2007, five false tsunami alarms were issued worldwide. Such alarms have negative societal and economic effects.

December 26, 2004
The 2004 Asian Tsunami was a disaster that affected many countries and killed hundreds of thousands of people. At 0:59 GMT on 26 December 2004, the India tectonic plate slid underneath its neighbor the Burma microplate, raising it by about 10 meters. The earthquake caused a powerful tsunami that was one of the deadliest in modern history and devastated coastlines around the Indian Ocean.

The earthquake had a magnitude of 9.0 and was the biggest since the Good Friday Earthquake off Alaska in 1964 which had a magnitude of 9.2. Entire towns were wiped from the map, more than 200,000 people were killed, and millions have been left in urgent need of food and shelter. The epicenter of the earthquake was near the island of Simeulu, off the west coast of Sumatra, Indonesia. The wave hit Indonesia and Thailand within an hour, and then Sri Lanka and India, and eventually reaching as far as eastern Africa. This tsunami destroyed most of the shores of Indonesia, Sri Lanka, South India, Thailand and other places with waves of 15 m (50 ft) high. It caused serious damage and deaths as far as the east coast of Africa

The word ‘Tsunami’ is of Japanese origin, which means, “harbour wave”. Tsunami are large waves that are generated when the see floor is deformed by seismic activity, vertically displacing the overlying water in the ocean. The quake occurred at a place where several massive geological plates push against each other with massive force. Tsunami has very low height while traveling over deep ocean. High waves occur only when it reaches the shallow waters, typically near the coast. The mega thrust earthquake-measuring 9.0 at Richter scale, off the western coast of northern Sumatra (Banda Ache), Indonesia was the largest of its type since the 9.2 magnitude Good Friday earthquake off Alaska in 1964.

The deadliest natural disaster caused by the tsunami generated from an undersea earthquake on 26 December 2004 in the Indian Ocean has shaken up the world. The 2004 tsunami generated waves of up to 15 meters in height and even hit Somalia at a distance of about 4500 km west of the epicenter. The tsunami traveled slowly and took seven hours to hit the farthest coast at the west. Because of the 1200 kilometer of the fault line affected by the seaquake was in a nearly north-south orientation, the greatest strength of the tsunami waves was in the east-west direction.

A pair of satellites that happened to be over the Indian Ocean just after the massive Sumatran earthquake on 26 December have captured the only measurements of the tsunamis’ height in deep water. The images will help improve future forecasts of the deadly waves.

The satellites did not observe coastal areas. But for eight minutes, they used radar to measure the sea level along a 3000-kilometre-long track of ocean. This image of the bay as the tsunami rolled through it provides a unique and valuable continuous measure of the waves. In contrast, the floating sensors suggested as part of any future early-warning system can only provide measurements at single points.

The satellites saw the first two wavefronts produced by the main quake, spaced 500 to 800 kilometres apart. These waves reached a maximum height of 50 centimetres in the open ocean, only reaching their full devastating height when entering the shallow waters of the coast.

By comparison, wind-driven waves typically reach 10 metres. However, these waves only involve water close to the ocean surface and are separated by at most several hundred metres.

Tsunami waves have a very deep reach indeed - 4000 metres or more. “These waves involve the entire depth of the ocean. Their energy is thousands of times more than a monster storm, they speed through the water as fast as jet airliners.

The key number in the modelling is wave height in deep water, as this indicates energy, and that is exactly what the radar recorded. Fu adds that, because the waves take time to travel to land, “when you see waves in the open ocean this large, you have time to warn people on the coast

An estimated 2 million people need food aid - overall food availability in the region adequate
11 January 2005, Rome — Local communities severely hit by the tsunami disaster will face severe food security problems in the short and long term because parents and relatives have been lost, livelihood assets have been destroyed, and sources of income no longer exist, FAO said today. Harvest prospects have deteriorated in agricultural areas worst hit by the tsunami and heavy rains.

FAO Director-General Dr Jacques Diouf met last Friday with ambassadors from affected countries and donors to evaluate the response to the emergency rehabilitation of fisheries and agriculture in affected countries.

Donors such as Belgium, the European Commission, Germany, Italy, Japan, Norway, Switzerland and the United Kingdom, amongst others, have already supported or expressed interest in FAO’s initial appeal for $26 million.

It is estimated that two million people in 12 different countries in the disaster region are in need of food assistance, FAO said. However, in spite of local losses, overall food availability in the region affected should be adequate to cover food needs.

“Since relatively large rice supplies are available in the region, it is recommended that local purchases be made whenever possible in order to meet food aid requirements in the different affected countries, so as to avoid domestic food markets disturbances,” said Henri Josserand, Chief of the Global Information and Early Warning Service.

However, given the damage to infrastructure, in particular roads, and the lack of suitable transportation means, logistical difficulties will hamper the distribution of food to the affected population.

Fisheries and agriculture in coastal areas have been severely hit by the tsunami waves. “Relief efforts must ensure that local farmers and fisher folk hit by the tsunamis receive all the assistance needed to cover their food needs and to restart farming and fishing as soon as possible. With international assistance, agriculture and fisheries should have the potential to recover from this catastrophe,” FAO said.

Impact on food security

In Indonesia all infrastructure has been destroyed in the worst-affected areas, leaving people without water, food or shelter. The provinces most affected by the tsunami, Aceh and Northern Sumatra on Sumatra Island, are among the most vulnerable areas in the country, with one-third of the population living below the poverty line.

The 2005 main season paddy and maize crops, to be harvested from March on, were already on the ground when the tsunami struck Sumatra. The island is the second in Indonesia in terms of rice production. Together, the two worst affected provinces account for about 10 percent of the aggregate national rice output in a normal year. There is currently no assessment of the impact of the tsunami on cereal production at local and national levels. Following last year’s bumper crop there are adequate stocks to cover the food needs of the affected population.

In Sri Lanka, the hardest-hit eastern and southern coastal districts are among the largest paddy growing areas. Planting of the 2005 main paddy season, accounting for some 60 percent of the total rice production, had just been completed when the tsunami arrived. In eastern parts, persistent heavy rains from mid-December and floods have also adversely affected the emerging paddy crop. Prospects for the harvest, scheduled to start in March, have deteriorated. The country’s already tight food supply situation could worsen further in 2005/06.

Thailand is the world’s largest rice exporter. With the harvest of the 2005 main rice crop just about to be completed, current rice supplies should be sufficient to cover the immediate food needs in the affected areas of both Thailand and neighboring countries.

In the Southern region, including the affected provinces, harvesting of the 2004 main season paddy crop was underway when the tsunami hit coastal areas. An assessment of the damage to agriculture is not yet available but local crop losses are likely. Since the whole Southern region accounts for only four percent of the country’s annual paddy crop, the damage is not expected to seriously affect production prospects at the national level.

In India, some 90 percent of the country’s annual paddy crop is grown from May to November. The tsunami did not affect the overall 2005 production prospects. Rice surplus is expected to be sufficient to cover the food aid needs in the country’s worst-affected areas.

In the Maldives, agriculture plays a minor role in the overall economy, due to the limited availability of arable land and shortages of domestic labor. The country’s cereal consumption requirements, averaging some 40 000 tonnes per year, are normally covered by commercial imports. However, the damage to housing and infrastructure in the tourism and fishing sectors will have a serious impact on the economy.