Volcanic eruptions are triggered in static dilatational strain fields generated by large earthquakes

Although data catalog analyses have confirmed that volcanic eruptions are triggered by large earthquakes, the triggering mechanism has been under discussion for many decades. In the present study, recent earthquake and volcanic data from the past 35–55 years were analyzed, and it was demonstrated for the first time that the likelihood of new eruptions increases two to three times in the 5–10 years following large earthquakes for volcanoes where the generated static dilatational strain exceeds 0.5 µ, which may, for example, activate gas bubble growth and thereby generate a buoyant force in the magma. In contrast, the eruption likelihood does not increase for volcanoes that are subjected to strong ground motion alone, which affect the magma system and volcanic edifice. These results indicate that we can evaluate the likelihood of triggered eruptions and prepare for new eruptions when a large earthquake occurs.