On 11 March 2011, Japan was hit by one of the strongest earthquakes ever recorded.
On 11 March 2011, Japan experienced one of the strongest earthquakes ever recorded. It measured 9.0 on the moment magnitude scale and struck beneath the Pacific Ocean, close to the country's north-east coast. The earthquake caused a huge tsunami, led to the Fukushima nuclear disaster and changed the lives of millions of people. It also did something that sounds almost unbelievable—it moved parts of Japan several metres to the east.
The reason for this lies beneath the Earth's surface. The outer layer of our planet is made up of enormous tectonic plates that move very slowly. Sometimes these plates become locked together while they continue pushing against each other. Over many years, accumulated pressure builds up. When the plates suddenly move, that stored energy is released as an earthquake.
The 2011 earthquake happened in a subduction zone. This is where one tectonic plate is pushed underneath another. During the earthquake, the seabed moved suddenly, and this displaced a huge amount of seawater. As a result, enormous tsunami waves travelled towards Japan's coast, causing widespread destruction.
Scientists used GPS technology to measure the effects of the earthquake. They discovered that parts of north-eastern Japan had moved about 2.4 metres to the east. The Japanese archipelago, which is made up of thousands of islands, had changed its position slightly. Although this movement was small on a global scale, it showed just how powerful the earthquake had been.
The earthquake even affected the whole planet. Scientists found that it slightly changed Earth's axis, the imaginary line that the planet spins around. This tiny change also made the length of a day a little shorter—by less than two millionths of a second. People cannot notice such a small difference, but scientists can measure it with very accurate equipment.
Japan is one of the best-prepared countries in the world for earthquakes. Many buildings are designed to move safely during strong shaking, and early warning systems can give people a few seconds to protect themselves. These systems saved many lives. However, the tsunami was much larger than many experts expected, and it caused far more damage than the earthquake itself.
After the disaster, Japan rebuilt many towns and improved its sea defences. Scientists also learned a great deal about earthquakes, tsunamis and how tectonic plates behave. This information is now used to improve safety in other parts of the world that are at risk of major earthquakes.
The 2011 earthquake reminds us that the Earth is always changing. Most of the time these changes happen so slowly that we never notice them. Sometimes, however, nature releases an enormous amount of energy in just a few minutes. When that happens, the results can be powerful enough to move an entire country.
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