The physical process governing the occurrence of the greatest explosive eruptions is characterized by a very high number of degrees of freedom. In this case, as well as for any stochastic and/or complex system, the knowledge of the process can be significantly improved by identifying any kind of nonrandom pattern. For example, a correlation with other processes would imply that some degrees of freedom are more important than the others. In this view, the main goal of this paper is to test if the perturbation induced on a volcanic area by great tectonic earthquakes can modify the probability of a volcanic event. The results obtained show that the occurrence of the largest explosive eruptions of the last century is significantly correlated to the earthquakes that occurred 0--5 and 30--35 years before, at distances up to 1000 km. Such a coupling might be attributed to the coseismic and postseismic stress diffusion. This result provides new insights that may be used in volcanic risk mitigation.