Insight on the Kilauea caldera evolution through the 2018 earthquake sequence

The deformation activity at the Kilauea summit and Lower East Rift Zone during the 2018 eruptive episode shows a tightly-connected magmatic plumbing system from the summit caldera to the lower rift zone. Using multiple approaches including seismic waveform analysis, moment tensor inversion, and infrasound simulation, we characterized the 62 M4.7+ events at the summit from 2018-05-17 to 2018-08-02 to infer the evolution of the magmatic reservoir and its impact on the caldera-rift system. We estimated that the first 12 events from 2018-05-17 to 2018-05-26 to be highly explosive and share the same source location as past explosions triggered by rockfalls. We inferred the source to be the previously-estimated Halema'uma'u reservoir at about 1 km depth, based on both seismic inversions and travel times of the infrasound signal. Once the reservoir has drained sufficiently and is no longer pressurized, the explosions ceased, and the caldera subsequently experienced partial collapse through a series of shallow normal-faulting events on the NW-N-NE edge, with small CLVD. Seismic and infrasound data also revealed an eastward migration of activities around 2018-06-25, coinciding with the change of surface deformation patterns observed independently by geodetic signals and radar imagery. The characterization of these large seismic events provides important constraints on the triggering mechanisms for the explosions and insight on the subsurface evolution of the Kilauea caldera.