Mega-quakes caused volcanoes to sink, research finds

Posted on July 1, 2013
A monitor displays the seismological chart of the earthquake which hit Japan on March 11, 2011 at the Geozentrum geological science center in Hanover, central Germany. Massive earthquakes can cause distant volcanoes to sink, according to research in Japan and Chile published on Sunday.

A monitor displays the seismological chart of the earthquake which hit Japan on March 11, 2011 at the Geozentrum geological science center in Hanover, central Germany. Massive earthquakes can cause distant volcanoes to sink, according to research in Japan and Chile published on Sunday.

Massive earthquakes can cause distant volcanoes to sink, according to research in Japan and Chile published on Sunday.

The magnitude 9.0 tsunami-generating quake that occurred off northeastern Japan in 2011 caused subsidence of up to 15 centimetres (9.3 inches) in a string of volcanoes on the island of Honshu as much as 200 kilometres (120 miles) from the epicentre, a Japanese study said.

And the 8.8-magnitude Maule quake in Chile in 2010 caused a similar degree of sinking in five volcanic regions located up to 220 km (130 miles) away, according to a US-led paper.

It was not clear whether the phenomenon boosted eruption risk, the authors wrote.

Both the Japan and Chile quakes were of the subduction type, caused when one part of Earth’s crust slides beneath another.

If the movement is not smooth, tension can build up over decades or centuries before it is suddenly released, sometimes with catastrophic effect.

In both cases, the sinking occurred in mountain ranges running horizontally to the quake.

The 2011 quake “caused east-west tension in eastern Japan,” Youichiro Takada of the Disaster Prevention Research Institute at Kyoto University told AFP in an email.

“Hot and soft rocks beneath the volcanoes, with magma at the centre, were horizontally stretched and vertically flattened. This deformation caused the volcanoes to subside.”

Read more at: Phys.org