Periodic slow earthquakes on the flank of Kīlauea volcano, Hawaiʻi

Abstract

We analyze 8 years of continuous GPS data from the Hilina slump (HS) on Kīlauea volcano's south flank and identify 3 new slow earthquake (SE) events. The new SEs are very similar to the previously identified one from November 2000, suggesting they share a common source. The series of SEs are separated by regular periods of 774 (± 7) days. None of the newly identified events are associated with increased rainfall rates, precluding rainfall as a necessary SE trigger. All of the SEs are followed by increased microseismicity in a ∼NW–SE trending band in the southern HS, suggesting that the SEs trigger seismicity. SE location and source parameters are not well-constrained by the CGPS network, although moment can be constrained adequately for the January 2005 event. Using this as a reference, we calculate for the four events equivalent moment magnitude values of 5.6, 5.7, 5.5, and 5.8, in their order of occurrence.