The March 2011 earthquake that decimated Japan and its Fukushima nuclear reactors with a monster tsunami altered the seafloor off the country’s eastern coast much more than scientists had thought. Analysis released today in the journal Science indicates the ocean bed moved as much as 50 meters laterally and 16 meters vertically.
Further reading here.
We detected and measured coseismic displacement caused by the 11 March 2011 Tohoku-Oki earthquake [moment magnitude (MW) 9.0] by using multibeam bathymetric surveys. The difference between bathymetric data acquired before and after the earthquake revealed that the displacement extended out to the axis of the Japan Trench, suggesting that the fault rupture reached the trench axis. The sea floor on the outermost landward area moved about 50 meters horizontally east-southeast and ~10 meters upward. The large horizontal displacement lifted the sea floor by up to 16 meters on the landward slope in addition to the vertical displacement.