Tohoku Earthquake

Fact File

  • Caused by a magnitude 9 earthquake
  • The wave reached South America within 21 hours; when it hit Chile, 17,000 km away, it was still 2 metres tall
  • The Earthquake started at 2:46PM on March 11th 2011, 24km below the surface and about 70km offshore
  • The shaking lasted around 6 minutes
  • The wave was up to 39 metres high and went up to 10 km inland
  • Around 561 km^2 were flooded
  • The first tsunami wave hit about an hour after the initial earthquake
  • The earthquake was large enough to just shorten the day (by a few microseconds) and slightly change Earth’s axis of rotation.
  • There were 5,000 aftershocks

Causes

Natural

  • The 2011 Tohoku earthquake struck offshore in a subduction zone in the crust, where the Pacific Plate descends beneath the Eurasian Plate
  • There was a clay layer lining the plate boundary, lubricating the fault. This allowed the crust to move a huge distance of around 50m in one go
  • According to the US geological Survey, around 400km of coastline dropped by 2 m from the quake, worsening the wave’s effects. Furthermore, this will have impacts on any subsequent tsunamis in the region’s impacts

Human

  • Japan is a very populated country, particularly along the East coast, where the wave approached from
  • Only 58% of people started heading to higher ground once they had a tsunami warning. The others assumed the tsunami would be small.
  • Around 100 tsunami evacuation sites were hit by the wave- they had not been built high up enough

Impacts

Short Term

  • Fukushima Daiichi Nuclear Power Plant suffered a level 7 nuclear meltdown, due to a cooling system failure caused by the water
  • The government estimated that US$300 x10^9 of damage was caused
  • The surge destroyed 3-storey buildings where people had gone to for shelter
  • 45,700 buildings and 230,000 vehicles were destroyed
  • Entire towns were wiped out
  • 15,891 people were confirmed to have died either immediately or from the flooding by April 10th 2015- most by drowning
  • In 3 days, and just one town, 1,000 bodies had already been found.
  • 1.5 million homes had no access to clean water supplies
  • 110,000 nesting birds were killed on island wildlife reserves throughout the pacific; a relatively minor impact compared to the impacts on Japan.

Middle Term

  • Access to power plants had to be stopped after the tsunami, due to fears that more of the nuclear power plants that Japan relies on for power would be leaking radioactive material. Some still remain closed.
  • Due to the shut down of their nuclear power plants, Japan had to use fossil fuels from outside the country, which cost vast amounts of money that could have gone to helping evacuees
  • Rolling blackouts occured due to loss of power generation, which only worsened the power situation, leading to a cyclical worsening situation until it was resolved
  • Public transport was largely unusable for a while
  • Tsunami seawalls were destroyed at several locations

Long Term

  • Areas near the powerplant got so irradiated that it will be uninhabitable to humans for up to thousands of years in the surroundings
  • In July 2013, TEPCO (Tokyo Electric Power COmpany) stated that around 300 tonnes of radioactive waste still leaks from the plant daily- 800,000 tonnes of contaminated water are stored in 1,000 tanks around the Fukushima site.
  • Radioactive material can be found washed up all along the Northern Pacific shoreline, especially the USA
  • Debris was still washing up on the USA’s shore two years later
  • Damaged buildings released many tones of greenhouse gases, which will impact climate change in the future
  • 230,000 people still are not in permanent housing; 180,000 evacuees (100,000 of which came from near Fukushima)
  • There are still around 2,500 missing people

Responses

Short Term

  • Japan has an early warning system which detects movements of the crust near to the fault line, and sends out an electric signal. The signal travels faster than the shockwave, which gave people about a minute’s warning of the shaking- the signal triggers alerts on phones and some TV sets.
  • The early warnign system also shuts off systems like nuclear power plants and trains, to help minimise the dangers of sudden shaking.
  • More than 160,000 people were evacuated from the coastlines after the tsunami had hit; 470,000 were evacuated from around Fukushima once it was clear there was a major issue with the system
  • Many countries sent search-and rescue teams; Japan deployed their self-defence forces, and worldwide charities supported the area. The Japanese Red Cross received US$1×10^9 in donations.

Middle Term

  • Researchers flooded in to measure activity and changes to the area around the moved faultline
  • Engineers also studied the collapsed buildings to learn more about how to earthquake and tsunami-proof buildings effectively.

Long Term

  • The government had made predictions of a smaller earthquake to occur around the same time, but they massively underestimated. However, they are still working to try to predict earthquakes to prepare in advance for them
  • Some geologists had found evidence that there was a tsunami of similar proportions in 893, and tried to warn the government of its scale, but they largely ignored the warnings they had about how large a tsunami might become

Evaluation of Responses

Japan had attempted to have a very varied range of responses to minimise the effects of tsunamis, and for the most part, they would have been effective. However, they were crippled by massive under estimates of the magnitude of the tsunami and the earthquake, and so provisions were made only for a far less serious disaster.

There was some degree of almost “casualisation” of earthquakes, leading to people not taking all available measures to keep themselves safe (most obviously staying on low land). Japan is generally very well equipped for earthquakes, which certainly greatly reduced the impact to the country as a whole.

 

References

http://www.livescience.com/39110-japan-2011-earthquake-tsunami-facts.html

http://www.ibtimes.co.uk/2011-japan-earthquake-tsunami-facts-about-devastating-event-that-killed-15800-1547423

http://www.bbc.co.uk/news/world-asia-35781593

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