Two volcanic eruptions in the Sumatra-Andaman arc that followed the disastrous M 9.3 earthquake of 26 December 2004 raise the question of whether these eruptions were triggered by the earthquake. Here we present new evidence to suggest that earthquake-induced decompression of the volcano magma systems leads to such eruptions. Numerical modeling reveals that other megathrust earthquakes induced volumetric expansion in the areas where vol canoes erupted. We suggest that abrupt decompression of a magma reservoir and/or its feeding system initiates processes that increase magma overpressure, and can ultimately lead to an eruption. Our evaluation of earthquake-induced deformation fields indicates which specific volcanoes are brought closer to eruption by earthquake rupture. Our analysis can provide important information for future volcanic risk evaluation in areas with regional fault systems prone to large magnitude earthquakes.