Case study - Indian Ocean Tsunami 2004

The causes and effects of the 2004 Asian Tsunami

A very common case study for earthquakes is the South-East Asian Tsunami of 2004. Other case studies include San Francisco 1989, Kobe 1995 and Haiti 2010.

The underlying causes

On 26 December 2004 there was a massive and sudden movement of the Earth’s crust under the Indian Ocean. This earthquake was recorded at magnitude 9 on the Richter Scale and as it happened under the ocean, caused a devastating sea wave called a tsunami.

The epicentre of the earthquake occurred 200 kilometres west of the island of Sumatra in the Indian Ocean. The earthquake itself was caused by the subduction of the Indo-Australian plate under the Eurasian plate.

As the Indian plate (part of the Indo-Australian plate) moved underneath the Burma plate (part of the Eurasian plate) the crustal rocks stuck as they moved past one another. At 08:00 local time, the pressure build-up was too great and the crustal rocks snapped, causing an earthquake.

When this happened the sea floor was pushed upwards, displacing a huge volume of water and creating the devastating tsunami waves.

Impact on landscape and population

Tsunami aftermath in Sri Lanka
Tsunami aftermath in Sri Lanka

Landscape

  • Some smaller islands in the Indian Ocean were completely destroyed.
  • Coastal buildings were flattened making people homeless.
  • Fishing villages were devastated.
  • Lines of communication, including phone lines, were cut off.
  • Electricity power lines were cut off.
  • Roads and railways were disintegrated.
  • Fires broke out due to severed gas pipes.

People

  • Approximately 250,000 people are estimated to have been killed, including many tourists on the beaches of Thailand.
  • There was an outbreak of diseases, such as cholera, due to a lack of fresh water supplies.
  • There was a lack of food as many fish died and farms were destroyed.
  • Thousands of people were made homeless.
  • Thousands of people lost their jobs as tourist hotels in Thailand were destroyed and fishing vessels were washed ashore.

Methods of prediction and planning

Earthquakes are extremely difficult to predict although scientists now know which areas have a higher risk of earthquakes and can identify frequency patterns from previous earthquakes.

As a result, active earthquake zones are closely monitored for seismic activity including the use of tiltmeters and laser equipment. They measure earth movements and sophisticated sound recording equipment to monitor earth tremors.

In developed countries such as the USA, constructing earthquake proof buildings, such as the Transamerica Pyramid in San Francisco which sways with the movement of the earth, has helped to reduce the damage caused by earthquakes.

Some countries practise earthquake drills, eg Tokyo in Japan, as routinely as we have fire drills and emergency services are better prepared and equipped to deal with such a disaster.

Despite all of these measures there were few warnings or successful predictions of the Indian Ocean Tsunami. Most of the countries affected were developing countries without the funds for these sophisticated methods of detection.

They also lacked the improved communications which might have allowed them to evacuate coastal areas in time. The only warning they received was the retreat of sea water from beaches before the wave hit.

Predicts the impact of a possible future tsunami in Padang, Sumatra

Question

Give methods used to predict and plan for an earthquake.

  • Seismometers are used to record seismic activity and any increased activity allows experts to plan ahead.
  • Sound recording equipment is used to monitor earth tremors.
  • Local authorities have emergency plans in place for evacuation, search and rescue.
  • Earthquake proof buildings which are designed to sway with the movement of the earth.
  • In Japan, people receive a text message to warn them of an earthquake.
  • Earthquake drills are regularly practiced to ensure people know how/where to evacuate.