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Bbc Bitesize Tsunami Case Study

Link to GCSE syllabus: A case study of a tsunami – its cause, effects and responses.

Case Study: The Tohoku Tsunami, Japan 2011

On the 11th March 2011 a powerful earthquake measuring 9.0 on the Richter scale occurred around 100km east of Sendai on Honshu, Japan, In just 30 minutes a wall of water up to 40m high hit the coast of north western Japan. It was followed in places by up to 9 additional waves up to 10m in height. 3000km of coastline was affected by the waves, which tore through coastal defences.

 

Map of earthquake locations.

Causes of a tsunami (BBC bitesize)

The earthquake that triggered the tsunami occurred at a destructive plate boundary where the Pacific plate was being subducted (pushed under)the North American plate. A segment of rock around 200km long slipped suddenly and flicked upwards by around 5-10m. This sudden uplift displaced (pushed up) the water creating the tsunami.

Effects

  • 200000 people killed
  • 500km2 coastal plains hit, destroying farmland, settlements and communications.
  • Ruptured gas pipes led to fires.
  • Explosions at the Fukushima nuclear power plant- this led to nuclear contamination and the possibility of meltdown as the cooling systems failed.
  • Electricity lost in 6 million homes, 1 million had no running water,
  • Further problems were caused by heavy snow and blocked roads.

Responses

  • 100,000 Japanese soldiers sent out to search and rescue.
  • Specialist search and rescue teams flown in from overseas.
  • Exclusion zone set up around Fukushoma, people evacuated from area.
  • Longer term: Re-building, re construction. Port facilities rebuilt, tsunami defence system reconsidered and extended.

 

Case study: Boxing Day Tsunami, 2004

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 1 metre high.
  • The tsunami travelled at speeds up to 800km per hour.
  • When the Tsunami reached the shores, the height of the wave increased to 15 metres in some areas.

Main 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.

Now try a Test Bite.

Map of Indian Ocean tsunami 2004

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