An active fault as long as 30 km may lie directly beneath Mount Fuji, a team of researchers has said in a recent survey report. The possible fault was detected through a simulated earthquake conducted during a crustal survey over a distance of around 34 km from Fujiyoshida in Yamanashi Prefecture to Susono in Shizuoka Prefecture, said Hiroshi Sato, professor at the Earthquake Research Institute at the University of Tokyo.

"More studies are needed to determine the depth and other details of the fault," Sato added. While faults have been confirmed around Mount Fuji, little is known about the seismic structure beneath Japan's highest mountain due to mudflows caused by a huge landslide that occurred around 2,600 to 2,900 years ago, as well as thick layers of volcanic ash. Mt. Fuji's last major eruption was 1707.

Investigation of underground structure by Ministry of Education, Culture, Sports, Science and Technology and Earthquake Research Institute of Tokyo University suggested that active fault runs for 30km directly under Mt.Fuji on 5/10/2012. This investigation was conducted from 2009 to 2011.

It may cause M7 class of earthquake to collapse the body of mountain by sediment and mud flow. This active fault may have caused the collapse of the mountain 2900 years ago.