Roger Musson, head of seismic hazard at the British Geological Survey, said there were similarities between the last week's disaster and another giant tsunami that hit the Sendai coast in 869, the BBC reported Tuesday.
Undersea earthquakes causing tsunamis in this part of Japan are not unusual, he said, and offshore temblors in the 19th and 20th centuries sent large waves against this area of coastline.
However, previous research by Japanese scientists shows that in the 869 "Jogan" disaster, tsunami waters moved some 2 1/2 miles inland, causing widespread flooding, as they did following the recent 9-magnitude earthquake.
Analysis of sediments from the Sendai coastal plain indicate the medieval-era tsunami was probably triggered by an 8.3-magnitude offshore quake.
Evidence of two earlier tsunamis on the scale of the Jogan disaster suggested there had been three massive events in the last 3,000 years.
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