Japan’s 11 March mega-quake shifted the ocean floor sideways by more than 20m (65ft), according one instrument placed on the seabed off the nation’s coast.
This direct measurement exceeds the displacement suggested by some models built only from data gathered on land.
The figure was recorded by the Japan Coast Guard which maintains underwater geodetic equipment along the fault responsible for the giant tremor.
An upwards movement of 3m (10ft) was registered by the same instrument.
Read the rest of the story: Instruments saw Japan quake lurch.