Increase in pressure in the deep magma reservoir detected prior to the 2018 Kīlauea eruption with ambient seismic noise interferometry

The recent Kīlauea eruption was one of the most devastating in recent history and lasted nearly 3 and a half months. Kīlauea is instrumented with a dense and modern geophysical monitoring system that is maintained by HVO, which provides an opportunity to study the behaviour of the volcanic edifice prior to eruption and to improve our ability to predict similar eruptions elsewhere. In this presentation we use ambient seismic noise interferometry to measure time-lapse changes in seismic velocity of the volcanic edifice prior to the 2018 Kīlauea Lower East Rift Zone eruption. GPS measurements at the summit showed that there was a slow inflation of the summit prior to the eruption. During the early stages of the inflation, the seismic velocity changes are directly related to the inflation (velocities increase during inflation and decrease during deflation). This observation is consistent with other recent observations. Roughly two weeks prior to a surge in seismic activity and the eventual eruption, the seismic velocities decrease rapidly even though the summit continues to inflate. We show that these effects are not likely to be due to movement of the southern flank or changes in the noise source distribution. The opposite effect of magma pressure on the seismic velocity changes are instead related to the depth of the magma reservoir. We argue that a decrease in seismic velocity while the summit is inflating is therefore a clear indication of increase in pressure of the deep reservoir, and could be a useful tool for forecasting volcanic eruptions. The recent devastating eruption highlighted the importance of improved forecasting of the time and intensity of impending eruption. Our results will have implications on forecasting volcanic eruptions and help to explain the dynamic processes that lead to eruptions.