Japan tsunami 'could be 1,000-year event'

Tsunamis on the scale that hit north-east Japan last week may strike the region about once every 1,000 years, a leading seismologist has said.

Dr Roger Musson said there were similarities between the last week's event and another giant wave that hit the Sendai coast in 869AD.

It is not unusual for undersea earthquakes to generate tsunamis in this part of Japan. Offshore quakes in the 19th and 20th centuries also caused large walls of water to hit this area of coastline.

But previous research by a Japanese team shows that in the 869 "Jogan" disaster, tsunami waters moved some 4km inland, causing widespread flooding.

The researchers said that such gigantic tsunamis occur in the area roughly once every 1,000 years. Dr Musson, who is the head of seismic hazard at the British Geological Survey (BGS), suggested the latest tsunami was comparable to the event in 869.

Quake rule
The most recent tsunami waves were up to 10m high; it is unclear how far inland the waters travelled, but reports say it was on the order of several miles.

Dr Musson told BBC News: "I would imagine it would be about the same, because it is hard to think that there would be any larger earthquakes than this in this part of the world."

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