Japan's Meteorological Agency on Friday, April 8, warned the country's 20 volcanoes has become alive due to the devastating March 11 earthquake, and a study said earthquake over 9.0-magnitude might hit Japan.

The Agency said volcanic explosion occurred after earthquake several times in history and people should maintain vigilance against this tendency, International Business Times reported.

The number of earthquakes above 6.0 M reached 77 on March. And 74 out of them occurred in quake-hit region, were aftershock. The number is 50 times over the same period last year.

The largest aftershock on April 7 hit Japan killed 4 people, injured at least 166, and caused a power outage over 2.61 million households, according to Japan's police officials. The Meteorological Agency warned aftershocks above 6.0 M like the April 7 earthquake probably would hit Japan again.

Meanwhile, quakes of the country's 20 volcanoes occurred more frequently after the March 11 earthquake, especially, the Fuji, Hakone, and Aso-San.

Authorities in Japan announced a research findings which indicated chain earthquake over 9.0-magnitude might hit Japan and its offshore area.

A massive 9.0 magnitude earthquake hit off the northeastern coast of Japan on March 11, 2011, triggering a massive tsunami which caused alerts to go up along the pacific basin. The National Police Agency reported at 10:00 a.m., April 8, the death toll rose to 12,731. The number of reported missing declined to 14,706.