Japan earthquake 2016 – where is Fukushima, what is a tsunami and how strong was the quake?
A magnitude 7.4 earthquake struck off the coast of Fukushima in Japan, and experts have said it is the aftershock to a devastating 9.0 quake in 2011 at the same site.
This aftershock hit at 5.59am local time on November 22, and so far no deaths have been reported, but injuries have occurred.
Where is Fukushima?
Fukushima is the capital city of Fukushima Prefecture, Japan, and was subject to a nuclear disaster in 2011.
It is in the norther part of Nakadori, the central region of the prefecture.
The city is near to mountains and is the location of the only Japan racing Association horse racing track in that region of Japan.
It has an estimated population of 290,064 in a total area of 746.43km.
What is a tsunami?
A tsunami, also called a seismic wave is a series of waves in a water body caused by the movement of a large body of water.
The killer waves can sometimes only be 30cm above the water surface when inn the open ocean, so go unnoticed by sailors
But as they reach shallower waters the wave is slowed down and the top of the wave moves faster than the bottom causing the sea to dramatically rise.
Tsunamis can cause the sea levels to rise by as much as 30 metres, although they usually cause a rise of three metres.
The enormous energy of a tsunami can life boulders, flip cars and plough down buildings.
Earthquakes, volcanic eruptions, underwater explosions, landslides, meteorite impacts and other disturbances above or below water can potentially generate a tsunami.
While normal waves are caused by the winds as well as the Moon and the Sun, a tsunami is always caused by the displacement of a large body of water.
What happened in 2011?
On March 11, 2011, an earthquake and tsunami occurred, with the earthquake affecting the city's water supply.
Train infrastructure was also severely damaged, and an energy accident took place at the city's Daiichi nuclear power plant.
This caused several explosions and the release of radioactive material.
A frozen soil barrier was constructed to prevent ongoing exposure of running groundwater with melted-down nuclear fuel.
Another strong earthquake occurred on April 7.
Experts say that the most recent quake and tsunami is the result of an aftershock of the 2011 disaster.
What happened in 2016?
A tsunami measuring one metre hit the coast at Japan’s Fukushima nuclear disaster site after a magnitude 6.9 earthquake.
It was the third wave to strike the coast after an earthquake hit the country at 6am local time.
The quake struck 117km east of Fukushima at a depth of 11km shortly after 6am local time on Tuesday morning (9pm GMT).
Cooling at the nuclear disaster site is thought to have been affected by the natural disaster, but the operator said there was no immediate danger.
Japan's chief cabinet secretary advised residents to leave coastal and riverside areas immediately.
So far no one has been killed by the events, but some injuries have been reported.
What happens now?
The Japan Meteorological Agency has warned another large quake could come in the next few days.
Tsunami warnings were issued at Fukushima and Miyagi prefectures, but have now been cancelled, with residents advised to avoid the shore.
The Daini nuclear power plant stopped operating in a reactor, but is running again. Work to decommission the Daiichi plant has been suspended.
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