The Chikyu, operated by the Japan Agency for Marine-Earth Science and Technology, was digging the seabed off Japan's north coast to take fault samples to study last year's earth- quake and tsunami, 'The Independent' reported.
According to the Canadian Press online, the Japanese vessel drilled into the fault zone at nearly 23,000 feet and continued drilling into the seabed last week.
Maritime organisations say the US vessel Glomar Challenger set the previous record of 23,130 feet below sea surface in the Mariana Trench in 1978.
The Mariana Trench is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about 2,550 kilometres long but has a mean width of only 69 kilometres.
It reaches a maximum-known depth of about 10.91 kilometres at the Challenger Deep, a small slot-shaped valley in its floor, at its southern end, although some unrepeated measurements place the deepest portion at 11.03 kilometres. PTI MOT
