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The period of heightened volcanic and seismic activity at Kīlauea volcano on the island of Hawai'i, USA from late spring through summer 2018 included a remarkable quasi‐periodic sequence of caldera collapse events. From mid‐May to early‐August, 62 collapse events, each releasing the seismic energy equivalent of a Mw 5.0 ± 0.4 earthquake, occurred about every 1–2 days with over 300 M ≥ 2.5 earthquakes between sequential collapses. This region, experiencing very high rates of seismicity and frequent large magnitude events, is a good candidate to apply a regional seismic hazard assessment. Nowcasting is a type of statistical analysis that uses small magnitude events to estimate the occurrence of large magnitude events. This is done utilizing the concept of natural time in which time is counted by small magnitude event occurrences between large magnitude events, not in clock time (days passed). This method has produced a "nowcasted" set of large earthquakes that are in good agreement with the actual cataloged events in prior studies analyzing non‐volcanic regions. Previously applied to tectonic earthquakes and induced seismicity over longer time frames, this is the first test of nowcasting large caldera collapse events in volcanic associated seismicity and on a relatively short time scale. The technique produced limited "success" nowcasting 37 collapse events that agreed with the catalog of actual events. A temporal dependence of successful nowcasting during the sequence was found that may correlate to previously identified and analyzed physical changes in the volcanic system. Key Points: We applied earthquake nowcasting to 37 caldera collapse events, yielding close agreement with the actual recorded set of collapse eventsKīlauea volcano saw a temporal change in the natural time relationship that can be related to changes in the physical systemThis nowcasting method revealed limited success in a volcanic setting compared to prior tectonic earthquake applications [ABSTRACT FROM AUTHOR]

Following the Mw 6.9 Hawaiian earthquake on 4 May 2018, a remarkable quasiperiodic sequence of collapse events began at Halema'uma'u Crater at the summit of Kīlauea Volcano. The collapse events were associated with the drainage of magma from beneath the summit to the Lower East Rift Zone where fissure eruptions occurred. From 4 June 2018 to 2 August 2018 forty‐seven collapse events Mw 5.3 ± 0.1 occurred with the same temporal pattern of seismicity occurring between sequential pairs of collapse events. This paper focuses on this interevent seismicity pattern. Following a collapse event, there was a relatively quiescent period. This was followed by a sudden increase in seismicity, occurring at a nearly linear rate of 397 ± 96 earthquakes per day. These seismically active periods lasted until the next collapse event occurred. The pattern then repeated itself beginning again with postcollapse quiescence. We provide a statistical summary of this seismicity behavior by isolating the quiescent and active times to look at immediate precollapse and postcollapse activity. In mid‐June there were significant changes in the quiescent time lengths (decreased), the number of earthquakes during the interevent times (increased), and the rates of seismicity during the active times (increased). This type of interevent study could be conducted with other seismically well recorded, sequential caldera collapse events and also with other data types to look for potential physical explanations and an improved understanding of precollapse and postcollapse activity. Key Points: The same pattern of seismically quiescent and active periods occurred between every pair of collapse events at the summitThe active times had linear rates of seismicity, and the quiescent times had fewer earthquakesFollowing a large increase in June 2018, there was a general decrease in the active time seismicity rates until the end of the sequence [ABSTRACT FROM AUTHOR]