Anatomy of a Caldera Collapse: Kīlauea 2018 Summit Seismicity Sequence in High Resolution

Abstract

AbstractThe 2018 Kīlauea eruption and caldera collapse generated intense cycles of seismicity tied to repeated large seismic (Mw ~ 5) collapse events associated with magma withdrawal from beneath the summit. To gain insight into the underlying dynamics and aid eruption response, we applied waveform‐based earthquake detection and double‐difference location as the eruption unfolded. Here, we augment these rapid results by grouping events based on patterns of correlation‐derived phase polarities across the network. From April 29 to August 6, bracketing the eruption, we used ~2,800 events cataloged by the Hawaiian Volcano Observatory to detect and precisely locate 44,000+ earthquakes. Resulting hypocentroids resolve complex, yet coherent structures, concentrated at shallow depths east of Halema'uma'u crater, beneath the eventual eastern perimeter of surface collapse. Based on a preponderance of dilatational P wave first motions and similarities with previously inferred dike structures, we hypothesize that failure was dominated by coupled shear and crack closure.