Japan: Huge quakes may have occurred at shorter intervals

Experts say massive earthquakes off Japan's Kanto region over the past thousands of years may have occurred at intervals far shorter than the government has estimated.

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A team of experts led by the National Institute of Advanced Industrial Science and Technology surveyed traces of quakes that occurred in Minamiboso City, about 100 kilometers south of Tokyo.

Quakes of about magnitude 8 repeatedly occurred along the Sagami Trough. Each quake raised the ground and moved the coastline.

Map of Sagami Through (Wikimedia/ Peka)

The team found the previously unknown trace of a coastline created 5,800 years ago. It also says 3 of the 4 known ones were 800 to 2,000 years newer than thought.

The team says the survey shows the coastlines were created by 5 quakes. The oldest one occurred 6,300 years ago and the newest one 314 years ago, and the shortest interval between quakes of this type was 500 years.

That’s one-fifth of about 2,300 years, the interval previously estimated by the government’s earthquake research task force. The team says the next huge quake may come sooner than expected.

Team member Masanobu Shishikura says a quake along the Sagami Trough could send a massive tsunami to the eastern part of the Boso Peninsula, and local authorities need to come up with measures to protect residents.

The government’s task force says it will use the findings as a reference when assessing earthquakes along the trough.

Source: NHK
Image: Wikimedia
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