Volcanic subsidence triggered by the 2011 Tohoku earthquake in Japan

The 2011 M-w 9.0 Tohoku earthquake caused an unprecedented level of crustal deformation in eastern parts of Japan(1-3). The event also induced seismic activity in the surrounding area, including some volcanic regions(4,5), but has not yet triggered any eruptions. Here we use data from satellite radar and the Global Positioning System to show that volcanic regions, located between 150 and 200 km from the rupture area(6), experienced subsidence coincident with the Tohoku earthquake. The volcanic regions subsided by 5-15 cm, forming elliptical depressions with horizontal dimensions of up to 15-20 km. The depressions are elongated in a direction roughly perpendicular to the axis of maximum coseismic extension. A high concentration of Late Cenozoic calderas(7), high heat flow(8), hot thermal waters(9), and young and hot granite(10) in the subsided regions imply the presence of magmatic and hot plutonic bodies beneath the volcanoes, that may have deformed and subsided in response to stress changes associated with the Tohoku earthquake along with the surrounding, thermally weakened host rocks. Similar subsidence observed in Chile following the 2010 Maule earthquake(11) indicates that earthquake-triggered subsidence could be widespread in active volcanic chains along subduction zones.