Tsunami History on Japan’s Honshu Island Sendai Coast

The triple disaster of earthquake, tsunami and nuclear reactor radioactivity releases following the 11 March M9.0 earthquake has a still-rising death toll and increasing health risks.  The Sendai Coast of Honshu Island, where the subduction zone has the Pacific Plate sliding under the Okhotsk Plate which carries northern Japan, has a well-known, long history of tsunami risk.  There were major tsunami from this plate boundary in: 869, 1611, 1793, 1856, 1896, 1933, 1952 and 1968.  The June 1896 tsunami from the  ~M8  Meiji-Sanriku earthquake on the section of subduction zone just north of the recent rupture killed about 22,000 people.  It had a run-up height of about 30 m – and the 1611 event was possibly even bigger!  A journal paper published in 2001 stated: “The recurrence interval for a large-scale tsunami {in this place} is 800 to 1100 years. More than 1100 years have passed since the Jõgan tsunami and, given the reoccurrence interval, the possibility of a large tsunami striking the Sendai Plain is high. Our numerical findings indicate that a tsunami similar to the Jõgan one would inundate the present coastal plain for about 2.5 to 3 km inland.”
It does seem at this early stage that the Japanese tsunami coastal defences [designed based on the 1896 event] were overtopped rather than destroyed and did mitigate the still catastrophic effects inland.  And, that even the 10 minutes provided by the tsunami warning system did allow many people to escape to higher ground.
Sources: K. Minoura et al. J. Nat. Disaster Sci. 23, 83–88; (2001); Nature News 17 March 2011; personal communications from Dr Alastair Barnett [Barncon Consultants] and Dr Rob Bell [NIWA].