Uplift and Seismicity Driven by Magmatic Inflation at Sierra Negra Volcano, Galápagos Islands

Although episodes of surface uplift and elevated seismicity precede many volcanic eruptions, their temporal evolution is often complex, apparently in contradiction to simple trends predicted by mechanical deformation models. Here, we use continuous global positioning system seismic data recorded at Sierra Negra volcano, Galápagos Islands, show how the edifice responded stress changes driven magma accumulation a shallow sill. The rate varied during 13 years 6.5 m inflation before 2018 eruption. number earthquakes per unit increased exponentially with total as differential increased. Accordingly, time function both rate. Gutenberg-Richter b-value decreased uplift. In final six months eruption, sequence large (M > 4) regulated state on fault, each being followed 2–3 days postseismic quiescence, retarding increase These did not affect overall Subsidence 8.5 accompanied 2-month On resumption uplift, was very low, high, reflecting relaxed fault system. observations that crustal becomes increasingly brittle higher states, supports theoretical models based elastic-brittle mechanics. They suggest joint interpretation key for forecasting future eruptions similar settings.