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Natural disasters of the Asia Pacific Region: Tsunami

Resources to support the Year 8 study natural disasters in the Asia Pacific Region.

Causes of tsunamis

     The name "tsunami" came from Japanese. It means harbor wave. It is usually caused by volcanic or earthquake activity under the ocean, sometimes it can also be caused by giant landslides.

      When an earthquake, volcano or landslide happens on the ocean floor, water is displaced. This water forms the start of the tsunami. When the waves reach shallower water:

  • their height can increase by several metres
  • the shallow water slows the wave
  • the waves get closer together

      The most obvious sign of a tsunami is the coastal water retreats just before the waves reach the shore. This is actually the trough of the wave following behind.

      Tsunami can eventually crash onto the shoreline. The effects on a community can be devastating.

Impact of tsunamis

   The main impact a tsunami has is flooding. The waters are also able to erode the foundations of coastal structures. The effects of the tsunami range from destruction and damage, death, injury, disease, environmental and financial cost, and long lasting psychological problems for the inhabitants of the region.

2013 Solomon Islands tsunami

Relief effort 2004 Tsunami

Acknowledgement

Animation of tsunamis

Animation of 2004 Indian Ocean tsunami

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Case study 1: 26/12/2004 Indian Ocean Tsunami

   On 26 December 2004 a tsunami occurred in the Indian Ocean. It was the result of the Indio-Australian Plate subducting below the Eurasian Plate. It was caused by an earthquake measuring more than magnitude 9. The earthquake caused the seafloor to uplift, displacing the seawater above.

  • In open ocean the tsunami measured less than 1m high.
  • The tsunami travelled at speeds up to 800km per hour.
  • When the Tsunami reached the shores, the height of the wave increased to 15m in some areas.

   

Facts & Impacts
A quarter of a million people died.
Two million people were made homeless.
People were swept away in the waters, which arrived rapidly and with little warning.
Thirteen countries were affected, the worst being Indonesia.
Indonesia was hit by the tsunami first. Fourty-five minutes later the tsunami reached Thailand.
Mangrove swamps helped to act as a barrier to reduce the energy of the water in some areas.
Short-term aid, such as water purification tablets, temporary housing and medical supplies were given from international countries.
Islands reliant on tourism and fishing, such as the Maldives, had to rebuild their industries.
An early warning system between countries surrounding the Indian Ocean has been set up.

Case study 2: 11/03/2011 Japan eathquake & tsunami

CASE STUDY SUMMARY
 
Date: 11 March, 2011
Primary Hazard: Earthquake (Magnitude = 9.0)
Secondary Hazards: Tsunami (average wave height 5-12m), Nuclear Meltdown
Areas Affected: North-East Japan, Tsunami: Pacific Basin
No of Deaths: 15,800 Approx
Buildings Destroyed: >125,000
People Displaced: >500,000
Economic Cost (Est.): US $235 Billion