Japan seabed shifted 24 meters after March quake

Last month's massive earthquake that devastated Japan's northeast shifted the seabed near the epicenter by 24 meters (79 ft), the coast guard said. The largest quake in Japan's recorded history also elevated the seabed off the coast of Miyagi prefecture by 3 meters, the coast guard said on Wednesday.

Sensors found that one part of the ocean floor had been stretched to a point 24m east-southeast of its position before the 9.0 undersea quake, which triggered a massive tsunami that engulfed large areas of Japan's northeast coast.

The undersea movement is more than four times bigger than any observed on land, where part of the Oshika peninsula in Miyagi prefecture was found to have shifted 5.3m.

The US Geological Survey (USGS) said in March that the force of the quake moved Honshu - Japan's main island - by 2.4m. The shift is seen from the image (left) of the shifting shoreline. Honshu Island is the largest island of Japan, which includes the city of Tokyo, Nagoya, Kyoto and Osaka.

“At this point, we know that one of the GPS station moved (8 feet), and we have seen a map of GSI (Geospatial Information Authority) in Japan showed a shift pattern over a large area that is consistent with the surrounding land,” said geophysicist of U.S. Geological Survey (USGS), Kenneth Hudnut.

The 9.0 magnitude quake was one of the biggest ever recorded. The movement is four times larger than any previous land shift recorded in Japan.

The quake and subsequent 10-meter tsunami left nearly 28,000 dead or missing in the northeast and triggered the world's worst nuclear disaster in 25 years at a power plant in Fukushima, 240 km (150 miles) north of Tokyo.

Source:
Reuters,"Japan seabed shifted 24 meters after March quake", accessed April 8, 2011
World News Co., "USGS: Earthquake in Japan Moves Honshu Island 2.4 Meters", accessed April 8, 2011