The ocean floor shifted sideways by 79 feet in the Japanese earthquake in March – much further than scientists originally predicted.
And researchers are warning that immense amounts of seismic stress remain stored in the area, putting it at risk of further devastating earthquakes.
The journal Science has published three new papers about the effects and causes of Japan’s March 11 mega-quake, which paints a picture of an earthquake hot spot much more complex and potentially dangerous than scientists had ever anticipated.
In one paper, the Japanese Coast Guard has released data from five geodetic instruments that in 2000-04 they had placed underwater along the fault line responsible for the colossal quake.
One of the instruments had actually been placed almost on top of the epicentre of the Magnitude 9.0 quake, at a station called MYGI.
Measurements taken in the week following the earthquake showed that at the MYGI site, the sea floor had moved about 79 feet to the east-southeast since the previous measurement in February. It had also risen about 10 feet.
Dr Mariko Sato, a geodesist with the Japan Coast Guard in Tokyo, believes almost all this movement happened during the quake.
‘The scale is almost double that estimated only from the terrestrial data,’ Dr Sato told BBC News.
Under the seabed, the movement may have been even greater – perhaps 160 to 200 feet, by some estimates.
In another study sure to raise alarm in Japan, scientists from the California Institute of Technology have reconstructed how the Tohuku-Oki earthquake unfolded using GPS data recorded at more than 1,200 sites.