For more than 1000 years, we have known that the seas off the coast of Sendai in Japan can turn treacherous. An account of how one quake unleashed a flood that swept away a castle town can be found in Nihon Sandai Jitsuroku (The True History of Three Reigns of Japan), completed in AD 901 for the emperor. (Editorial)

http://www.newscientist.com/article/mg21028092.500-time-to-rethink-megaquakes.html