Probing magma storage during the May 2018 eruption using coupled dike-chamber models

Compared to the previous 50+ dike intrusions that have occurred at Kīlauea Volcano, the May 2018 eruption of the lower east rift zone (LERZ) is distinguished by the anomalously distal location of the dike intrusion and eruption relative to the summit, the large eruptive volume, and caldera collapse. The location of the dike, the collapse of the Pu`u `Ō`ō crater, and the exponential deflation at Pu`u `Ō`ō recorded by tiltmeter compared with the more gradual linear deflation at the summit within the first few days all suggest that the dike was initially fed by a reservoir of magma beneath Pu`u `Ō`ō and later by the shallow summit chamber. We use coupled chamber-dike forward models to perform a Bayesian joint inversion of time series data including tiltmeter, seismicity in the LERZ, and lava lake levels in Halema'uma'u, with a Markov chain Monte Carlo (MCMC) approach to estimate the volumes and hydraulic connectivity of magma sources in the summit and LERZ. We find values for the summit chamber volume and magma compressibility that are in agreement with other studies. Furthermore, we find that the distal location of the dike alone cannot explain the data unless there is a magma chamber located beneath Pu`u `Ō`ō that contributed to the dike supply. This work suggests that the location of dike initiation and the sources of magma tapped by diking significantly influence the resulting dynamics and size of eruptions.