SENDAI, JAPAN (BNO NEWS) -- Scientists have discovered evidence that a massive tsunami has hit the eastern coast of Japan every 1,000 years, the Daily Yomiuri newspaper reported on Thursday.

Sediment found in strata of a cliff in Kesennuma of Miyagi Prefecture indicates that a massive tsunami of at least 10 meters (33 feet) high has hit the Sanriku coast six times during the past 6,000 years.

The discovery was made by a team of scientists led by Kazuomi Hirakawa, a special appointment professor at Hokkaido University and an expert in geomorphology, at Oya beach in the city of Kesennuma, which was devastated by the March 11 earthquake and resulting tsunami.

Hirakawa said the traces suggest the region has been hit every 1,000 years or so by an earthquake with an estimated magnitude of 9 on the Richter scale, similar to this year's deadly earthquake.

Hirakawa and his research team examined the cliff in April and May this year for layers from the past 6,000 years to check whether they contained materials such as sand, shells and even large stones that are carried inland from the sea by a tsunami and deposited on the ground as it recedes.

As the cliff is located about three meters (10 feet) above sea level, no sediment should have been left by tsunamis only a few meters high, according to Hirakawa as cited by the newspaper.

The research team found six layers of sediment and estimated the time each layer was created based on clues such as volcanic ash known to date from about 5,400 years ago.

According to the scientists' estimate, a tsunami caused by the Jogan earthquake hit the Sanriku coast in 869 followed by the one triggered by the Keicho earthquake in 1611.

On March 11, a 9.0-magnitude earthquake hit the eastern coast of Japan and caused tsunami waves of up to 40.5 meters (133 feet) in the Tohoku region. In some cases water traveled up to 10 kilometers (6 miles) inland. The disaster killed at least 23,482 people, while 8,069 remain missing.

It is hoped the discovery will be useful in reviewing disaster management plans by Japanese central and local governments.

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