In two unrelated studies, Youichiro Takada and Yo Fukushima of Kyoto University and Matthew Pritchard and colleagues of Cornell University used satellite data to analyze the deformation of Earth's surface caused by the 2011 magnitude 9 Tohoku earthquake in Japan and the 2010 magnitude 8.8 Maule earthquake in Chile, respectively.
Following both of those earthquakes, volcanoes situated near the ruptured faults subsided by almost 6 inches, the researchers reported in the journal Geoscience.
The effect may occur in most big earthquakes, they said.
"There's every reason to suspect this is a widespread feature," Pritchard said.
Nobody had noticed the subsidence before because satellite imaging was not sensitive enough to detect it, he said.
Pritchard, who studied the Chilean quakes, said he suspects the shaking opens cracks in the rock, allowing water trapped underground to escape to the surface in hot springs, and triggering subsidence.
Takada and Fukushima, on the other hand, say they suspect volcanoes' magma chambers can be deformed by quakes, allowing the rock above to settle.