Tsunami in Japan ‘may return after 1000 years’
March 16th, 2011 - 12:11 pm ICT by ANILondon, Mar 16 (ANI): Tsunamis that hit north-east Japan last week are likely to strike the region once every 1000 years, suggests an expert.
Roger Musson, a leading seismologist, has said that 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. 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.
“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,” the BBC quoted Musson as saying.
The BGS seismologist acknowledged there had been other notably large earthquakes in the region in 1933 and in the 1890s.
But he said: “There is a convenient little fact to remember… if you know how often Magnitude 9 earthquakes are, you will get Magnitude 8 earthquakes roughly 10 times as often and Magnitude 7 earthquakes approximately 100 times as often.”
However, another researcher said they would be cautious to draw conclusions about the frequency of such events, given how seismically active this region is.
About 10 years ago, a team led by Koji Minoura, from Japan’s Tohoku University, analysed sediments from the Sendai and Soma coastal plains that preserved traces of the tsunami in 869.
Their results indicated that the medieval tsunami was probably triggered by a Magnitude 8.3 offshore quake and that waters spread more than four km from the shore.
They also found evidence of two earlier tsunamis on the scale of the Jogan disaster, leading them to conclude that there had been three massive events in the last 3,000 years. (ANI)
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Tags: 1890s, 19th and 20th centuries, bgs, british geological survey, coastal plains, east japan, giant wave, japanese team, jogan, magnitude 9, minoura, musson, previous research, quakes, seismic hazard, seismologist, tohoku, tohoku university, tsunami in japan, undersea earthquakes