An active fault around 200 km long that is believed to have been a source of huge quakes in the past has been found off Honshu's Kii Peninsula, according to researchers at the University of Tokyo.

If the fault on the Nankai Trough moves, it could trigger a magnitude 8.0 earthquake, the researchers said, adding they have found a seabed cliff several hundred meters high that was created by the fault's past movements.