Japan… article updated.

Earthquake and tsunami

Unless you’ve been hiding under your pillow for the last few days you must have heard of the magnitude 8.9 9 Earthquake that happened under the ocean near Japan, causing a massive Tsunami that flooded much of the coast.

Here you can see footage of the

And here you can see pictures of the damage by sliding the bar to see the before and after pictures.

You can see from this diagram why the tsunami killed so many people – the earthquake was so close to the shore there was only minutes to warn and evaquate people.

The earthquake even reached the UK, my old university (Keele) recorded the earthquake using their seismometers, it was so big it still went off the scale half the world away.

The full details of the earthquake can be found here on the usgs.com website

The first episode of the new series of BBC’s Bang Goes the Theory was dedicated to the science behind the Japan earthquake and tsunami. You can watch it on iPlayer here.

Here is a clip from the episode showing how earthquake build up so much energy and how tsunami are formed when the seabed shifts suddenly.

Japan has a good record of designing buildings that can survive earthquakes, as can been seen in the video. Wooden buildings are generally good because they can flex without breaking. But a tsunami is a different proposition – with a large mass of water flowing through them few buildings can survive.

Nuclear Reactor

During the earthquake Japans nuclear reactors were shut down. Control rods moved in to stop the reactions, but nuclear reactors get very hot and it takes days and weeks to cool them down. Unfortunately it is the cooling of the reactors that has been the problem. Water pumps have been damaged, so the coolant inside the reactors has been boiling, needing releases of pressure that have taken small amounts of radioactive material with them. Some of these pressure releases exploded – the coolant water having split into hydrogen and oxygen. If the coolant falls below the level of the fuel rods, the fuel rods can over heat and start to melt – this is called a melt down.

As long as the main case of the reactor is not damaged then the bulk of the radioactive material remains safe. Only tiny amounts have been released with the steam (still en0ugh to be over legal limits, but nothing like the dangerous levels seen after Chernobyl exploded). Keep updated

Updates…

  • This Telegraph article gives numbers that highlight the scale of the earthquakes effects
  • This BBC page shows the stages the nuclear power plant has gone through and answers some questions about the radioactivity – including discussing the risks and comparing it to Chernobyl
  • The video below illustrates what has been going on with the reactor

Mr G

Sources: BBC News, ABC News, MSNBC, BBC iPlayer, Hypocentral.com,  usgs.gov, Telegraph

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