TOKYO - Last month's massive earthquake that devastated Japan's northeast shifted the seabed near the epicentre by 24 metres (79 ft), the coast guard said.

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 largest quake in Japan's recorded history also elevated the seabed off the coast of Miyagi prefecture by 3 metres, the coast guard said on Wednesday.    

The quake and subsequent 10-metre 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.