Infrasound observations and constraints on the 2018 eruption of Kīlauea Volcano, Hawaii

The 2018 eruption of Kīlauea Volcano was a dynamic event involving explosions, collapses, and fountaining at multiple vents spread over tens of kilometers. The permanent infrasound network operated by the USGS Hawaiian Volcano Observatory (HVO) was well prepared to observe the collapse of the summit, and additional deployments permitted infrasound observations during fissuring in the lower East Rift Zone (LERZ). We provide a summary of infrasound observations, including lava lake spattering, collapses, explosions, rockfall, and lava fountaining, using seismicity and tilt at times to help constrain our interpretations. At the summit of Kīlauea Volcano, we document the process of partial caldera collapse and examine a set of “proto-collapse” events that precede the widely observed events but share many of the same qualities as the larger collapses. For the initial twelve collapse events, we compare the timing of collapse onset to other observations and illustrate the repeatable characteristics of the recorded waveforms and infrasound characteristics associated with each episode of caldera collapse. In the LERZ, we match the acoustic signals with visual observations, including fissure migration, explosions near fissures, and littoral explosions. Lastly, we document and discuss the performance of infrasound alarms during the 2018 Kīlauea eruption. In general, alarming became successful in detecting collapse events at the summit of the volcano after tuning and became a key discriminant in the initial determination of collapse events, especially when visual observations were not available.