It was the biggest quake to rock Japan in recorded history. On 11 March 2011, just 130 km off the coast of Sendai, on the main island of Honshu, a section of the massive submarine fault separating the enormous Pacific plate from northern Japan failed.
In a few minutes, over 500 km of the fault catastrophically ruptured, and rocks on either side were thrown over 20 metres along the fault.
The island of Honshu was wrenched 2.5 m towards the east, and the Earth's tilt axis moved by 16 cm in response to this enormous redistribution of mass. The seafloor upheaval shunted a column of water over 6 km deep upwards - a massive disturbance which culminated in a 10 m tsunami swamping the Japanese coastline.
At magnitude 9, the quake was propelled into another class of monster - a megaquake. The scale used to measure earthquake magnitude, whilst useful, does not do justice to the energy involved in the biggest of the big.
The moment magnitude scale is logarithmic - meaning the energy released by a magnitude 9 is around 32 times greater than a magnitude 8, and almost 1,000 times larger than a magnitude 7.
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