Ocean floors certainly change with earthquakes - this was dramatically shown after the Kaikoura quake here in NZ.
http://www.sciencealert.com/new-zeal...s-above-ground
The small tourist launch basin floor rose, stranding most of the whale-watching boats. Frantic work was undertaken to get the boats (Kaikoura's money earner) operational. The navy did a quick survey to allow access for relief aid boats plus an area offshore for relief ships to anchor. A detailed hydrographic survey from Cook Strait to Banks Peninsula is planned - the area at present being subject to a Notice to Mariners warning of possible depth variation to those charted.
Dennis.