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11th March 2011 Japanese Earthquake: A Case Study



March 2011 Japanese Earthquake/Tsunami:

When?
11 March 2011, 2:46PM local time.

Where?
The earthquake occurred 250 miles off the North East coast of Japan's main island, Honshu. 

What?
An earthquake measuring 9.0 on the Richter Scale struck off Japan's north-east coast, about 250km from Tokyo at a depth of 20 miles.

Why?
The Eurasian plate is being subducted by the heavier, denser Pacific plate at a destructive plate boundary. The Eurasian plate whilst being subducted by the oceanic Pacific Ocean plate caused immense pressure to build up, which eventually caused the plate to buckle and spring back up lifting up a huge volume of water that made the tsunami.
  • Sendai was the first area hit by the earthquake, with S waves (Secondary waves) travelling at a speed of 3km per second from the epicentre.
  • Fukashima (150km away from the epicentre) the warning system immediately shut down the nuclear reactors but were not able to cool down properly.
  • L waves (Surface waves) reached Tokyo (citizens were given a 60 seconds warning through SMS, televised and radio warnings about the earthquake), they braced themselves for the earthquake but were not prepared for 5 minutes of ground shaking (ground shaking during earthquakes usually lasts less than 1 minute.)
  • After the quake, minutes later a tsunami was expected to hit the north-east coast.
  • The buckling of the Eurasian plate lifted a 6km long wave of water that sped towards the Japanese coast, travelling at around 800kmph.
  • Ofunato, in the Iwate Prefacture, was the first area to be hit by the tsunami.
  • In Miyako, also in the Iwate Prefacture, regular tsunami warning drills are carried out so that citizens know what to do in the event of a tsunami striking. They believed that their sea walls, which were 10m high, would be able to stop the tsunami, but the waves were a similar size and easily went over the top of the wall.
  • The 9.0 magnitude earthquake was strong enough to cause the coastline to sink by 1m, which effectively made the Miyako sea walls 9m high instead of 10m high.
  • 40 minutes after the earthquake, Fukashima Nuclear Power Plant was hit by the tsunami, which caused a nuclear meltdown which prompted the closure of all nuclear power stations in Japan in May 2012.
  • A 6.2 magnitude aftershock struck Tokyo.
  • There were approximately 500 aftershocks for a week following the main 9.0 earthquake.
  • Approximately 20,000 people died as a result of the earthquake and tsunami.

Tags: [a2] geography
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