One of the blog sites that I visit daily is Volcano Live by John Seach a note volcano photographer. John hosts the world's first volcano news and travel website, which monitors worldwide volcanic activity, and provides adventure tours to the world's most exciting volcanoes. Volcano eruptions have been associated with historic climate changes and they need to be considered when assessing future changes, which is a hobby interest of mine.
John had this to say about the Great Japan Earthquake and it's potential impact on volcanic eruptions.
The Great Japan Earthquake of 2011 (mag 8.9 9.0) and its aftershocks, are capable [of] disrupting volcanoes large distances from the epicentre. Very large eruptions are possible after Great Earthquakes. It is possible for eruptions to occur anytime after the earthquake, and the high risk period will last for several months. Japan contains ten percent of the world's active volcanoes. The closest active volcano to the earthquake is Narugo, 150 km WNW of the epicentre. Volcanoes near to the earthquake epicentre include:
Kurikoma (153 km), Zao (170 km), Hijiori (195 km), Azuma (200 km), Adatara (200 km), Iwate (205 km), Akita-Komaga-take (210 km), Bandai (220 km), Chokai (220 km), Hachimantai (223 km), Akita-Yake-yama (228 km), and Nasu (250 km). [Complete list of Japan's volcanos is here.]
The aftershocks are migrating south and now are within 70 km of Tokyo and 200 km of Mt Fuji volcano. Mt Fuji last erupted in 1708.
I was curious to see if the Mt Fuji eruption in 1708 was associated with a large earthquake, and I found this on the Internet:
The notorious last eruption of Mt. Fuji began with a huge earthquake on November 11, 1707. For miles around the epicenter, Japanese people felt the effects of this earthquake, particularly in the city of Osaka. People knew that Mt. Fuji could be expected to blow at any time, but the explosion was no less than historic.
The Great Hoei Eruption, as it is now known, occurred between mid-December and early January of 1707-1708, causing earthquake-like tremors for miles around and strewing huge amounts of ash and cinder. On the fateful day of December 16, 1707, Mt. Fuji began belching up ash and cinder. The explosions continued for a period of more than two weeks, spitting up hundreds of millions of cubic feet of volcanic ash, which was spread for miles and miles to the east of the mountain.
To put the range of the explosion into context, ash even fell in the city of Tokyo nearly 90 miles away! This eruption is still remembered today for its notoriety, which created three new vent holes in the volcanic mountain.
There seems to be a delayed reaction between the earth quake and a future eruption. As one scientist explained, huge earth quakes cause the magma to slosh about below the earth's crust and then when the waves of magma combine, they fill the chambers under volcanoes and which can start it erupting. There my be more disaster on the horizon for Japan. Stay tuned.
Exit Question: Do you think that a 9.0 earth quake will cause near by volcanoes to erupt?
Update (03-15-11, 22:00) A large, shallow earthquake (mag 6.2) occurred under the SSW flank of Mt Fuji on 15th March 2011.
Mt Fuji Volcano Eruptions: 1707-08, 1700, 1627?, 1560, 1511, 1427?, 1083, 1032, 1017?, 999?, 993?, 952?, 937?, 932, 870, 864-65, 830, 826, 802, 800, 781.