This is astounding. Paul Rincon reports for BBC News:
Japan’s coastline may have shifted by as much as 4m (13 ft) to the east following Friday’s 8.9 Magnitude earthquake, according to experts.
Data from the country’s Geonet network of around 1,200 GPS monitoring stations suggest a large displacement following the massive quake.
Dr Roger Musson from the British Geological Survey (BGS) told BBC News the movement observed following the quake was “in line with what you get when you have an earthquake this big”.
The quake probably shifted Earth on its axis by about 6.5 inches (16.5cm) and caused the planet to rotate somewhat faster, shortening the length of the day by about 1.8 millionths of a second.
Japan’s meteorological agency has proposed updating the magnitude of the earthquake to 9.0. [UPDATE: Has been changed to 9.0] This would make it the joint fifth biggest quake since instrumental records began, but other agencies have not yet followed suit.