2011 earthquake put pressure on Mt. Fuji

The magma chamber under Japan's Mount Fuji felt so much pressure during a March 2011 earthquake and one of its aftershocks it could erupt, researchers said. Pressure increases are not the only factor involved in eruptions, however, and no signs of a pending eruption have been detected, officials at Japan's National Research Institute for Earth Science and Disaster Prevention said. Mount Fuji has not erupted since 1707, but the same circumstances of a rise in pressure caused by a preceding earthquake were present then, the researchers said. The magnitude-9 quake that struck off the coast in March 2011 and a magnitude-6.4 aftershock four days later increased the pressure on the magma chamber, thought to be some 10 miles underground. Although conditions in the magma chamber vary, the recorded pressure increase is "not a small figure," Eisuke Fujita, a senior researcher at the institute, told Kyodo News.