Volcano–tectonic interactions as triggers of volcanic eruptions

Abstract

Surface displacements and edifice deformations at active volcanoes can occur when magma reservoirs begin to inflate as new magma enters them. Volcanoes are also subjected to a variety of external lithospheric stresses that are thought to be responsible for triggering volcanic unrest or modifying ongoing activity. However, despite many observations, it is uncertain whether these phenomena can actually interfere with magma chamber dynamics since it is not clear why some volcanoes are more subjected to these interactions than others. In order to determine whether external stresses interfere with volcanic activity, a viscoelastic 3D Finite Element Mogi-based model of Kīlauea volcano's magma chamber was implemented. First, the model was used to replicate an inflation cycle without external stresses. Its results were then compared with the ones obtained if the same model was subjected to tidal stress modulation and a strong (Mw=7.7) tectonic earthquake. The model showed that tidally-induced pressurization is not sufficiently large to modify the pressure in a 5km deep volcanic magma chamber, but it suggested how the magma chamber pressure build-up rate can be influenced by tidal pressurization and thus why some volcanoes seem to experience tidal interferences more than others. Furthermore, the model's results suggested why magma chambers are about the same size as calderas both on the Earth and on other Solar System silicate planets. System. Finally, it was used to propose an explanation of why a short-lived eruption at Kīlauea volcano, Hawai’i, began 30min after the 1975 magnitude 7.7 (Mw) Kalapana earthquake.