Tsunamis

A tsunami is most often triggered by undersea earthquakes that cause massive changes to the ocean floor.  Tsunami can also be caused by seismic events, landslides, or even asteroid impacts (http://www.ema.gov.au)

Cause When an undersea earthquake or other major disturbance causes a section of the ocean floor to suddenly rise or sink, the mass of water above the affected area also rises or sinks. This unexpected movement of the water creates a series of powerful waves.

Undersea earthquakes that cause massive changes to the ocean floor and the displacement of a large volume of water are the most common cause of a tsunami.

Tsunami can also be caused by other undersea events such as volcanoes or landslides.

A tsunami can also be caused from events above the ocean floor. These events could include a meteorite crashing into the ocean, major landslides near a coastline or material from an erupting volcano forming a landslide. The impacts of tsunami triggered this way tend to be localised.

More than 75 per cent of tsunami are caused by undersea earthquakes. (http://www.ema.gov.au)

Effects

A tsunami reached the Australian coast at Steep Point on 17 July 2006 generated by a magnitude 7.7 earthquake south of Java. The tsunami caused widespread erosion of roads and sand dunes, extensive vegetation damage and destroyed several campsites up to 200 metres inland. The tsunami also transported a 4WD vehicle ten metres. Fish, starfish, corals and sea urchins were deposited on roads and sand dunes well above the regular high-tide mark. (www.ga.gov.au)

The tremendous energy of the wave can cause great quantities of water to surge inland, far beyond where even the highest of tides would commonly reach.

Some of the largest tsunami waves have been generated by the volcanic eruption of Krakatoa in 1883. This tsunami reached a height of 37 m. In 1737, a tsunami was estimated to be 64 m high as it struck Cape Lopatka in northeast Russia. (http://www.ema.gov.au)

Economics

Boxing Day 2005 marked the first anniversary of the tsunami that devastated communities in Indonesia, Thailand, Sri Lanka, India and as far away as the east coast of Africa, leaving an estimated 230,000 people dead and 1.7 million displaced. Australia has provided substantial assistance to the tsunami-affected countries, with the main focus of our effort on one of our nearest and largest neighbours, Indonesia. The $1 billion Australia-Indonesia Partnership for Reconstruction and Development (AIPRD), announced by Prime Minister Howard on 10 January 2005, is the single-largest aid package in Australia’s history. The Australian Treasury has worked with the Australian Agency for International Development (AusAID) and other Australian Government agencies to develop and implement the AIPRD, and the Treasurer is one of the five Australian and Indonesian Ministers on the AIPRD Joint Commission. (http://www.treasury.gov.au)

http://www.aph.gov.au

Geography

Most tsunami occur in the Pacific and Indian Oceans. The boundary of the Pacific Ocean experiences frequent earthquakes. This boundary is commonly known as the Ring of Fire. There are two major subduction zones in the Indian Ocean that can also generate tsunami.

Subduction zone earthquakes are the most common source of destructive tsunami. These earthquakes are generated when two tectonic plates meet and one goes under the other, usually at a rate measured in centimetres. The sinking (subducting) plate drags against the upper plate, causing flexing. Continued stress on the plate boundary results in the upper plate rebounding to its original position, displacing the sea water above. (http://www.ema.gov.au)

Historical

South Pacific Tsunami Event 29 September 2009

Observed water heights and calculated tsunami travel times, 29 Sept 2009	Pago Pago harbor, American Samoa

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Chile Tsunami Event 27 February 2010

Observed water heights and calculated tsunami travel times, 11 March 2011	Dichato, Chile

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Japan Tsunami Event 11 March 2011

Observed water heights and calculated tsunami travel times, 11 March 2011	Minami Sanriku, Japan

(http://itic.ioc-unesco.org/)

Solomon Islands tsunami 2 April 2007

On 2 April 2007 an earthquake measuring 8.1 on the Richter Scale had its epicentre 350 km NW of Honiara. The earthquake occurred in shallow water in the early morning and was quickly followed by a tsunami. The waves were up to 10 m high. Over 50 deaths were reported and thousands were left homeless. A tsunami warning was issued for Australia and Alaska 15 minutes after the earthquake. 

Indian Ocean tsunami, 26 December 2004

This event was one of the most devastating caused by a natural hazard in recent years. The earthquake that triggered the tsunami occurred west of the Indonesian island of Sumatra and measured 9.0 on the Richter Scale, making it the largest earthquake worldwide in 40 years. The death toll in March 2005 was over 273 000 people, with many still missing.

Papua New Guinea tsunami 17 July 1998

An earthquake measuring 7.0 on the Richter Scale just off the northern coast generated a destructive tsunami. Waves up to 10 m high hit the villages in the Aitape region extremely quickly. More than 2000 people were killed and there was great damage to buildings and farmland.

(http://www.ema.gov.au)

Community response

Wahroonga, New South Wales — The Adventist Development and Relief Agency (ADRA) Australia has contributed to an ADRA network-wide response to the earthquake which struck Yogyakarta Province, in Central Java, Indonesia on 27 May.

ADRA has emergency response teams already on the ground on Java Island and is rushing additional emergency staff into the affected region.

ADRA Australia’s contribution is part of an initial ADRA network-wide allocation of just over US$100,000 to get relief efforts underway immediately. Fund are intended to provide tents/shelter, medical care and supplies, mats, blankets, sarongs, hygiene items, food kits and cooking supplies for affected families and psychological support for affected children. A Seventh-day Adventist Church in the hard-hit subdistrict of Bantul has been opened as a shelter for displaced families. ADRA will work in collaboration with other non-governmental organisations (NGOs) and the UN to expand its response efforts in the coming days.

(http://www.adra.org.au)

Government response

At a news conference in Sydney on 27 December, the Prime Minister said: 'I express on behalf of all of the Australian people my deepest sympathy and great profound condolences to the people and the governments of so many countries in our region. The Australian people feel the greatest sympathy for our friends in the region. We'll do everything we can as a regional neighbour and regional friend to assist the countries that have been so badly affected.'

While the magnitude of the disaster was still unfolding, the relief effort began immediately in Canberra and posts in countries in affected areas.

In the first 36 hours following the disaster:

• an emergency task force of senior officials was established in Canberra at 6 pm on Sunday 26 December to coordinate Australia's response
• the AusAssist Plan, a standing AusAID disaster response plan, was activated on 27 December 2004
• essential supplies from the AusAID emergency store were sent to Indonesia on four RAAF C-130 Hercules, departing on 27-29 December
• the flights also took two AusAID funded medical teams to conduct health assessments and provide primary treatment
• AusAID funded the immediate deployment of four participants in United Nations Disaster Assessment and Coordination (UNDAC) teams to Thailand and Indonesia
• AusAID staff from posts in affected countries were dispatched to disaster areas to assess the impact of the tsunami
• additional staff from Canberra were sent to Indonesia, Thailand and Sri Lanka to support post. (http://www.ausaid.gov.au)