Inter-Event Seismicity Statistics Associated With the 2018 Quasi-Periodic Collapse Events at Kīlauea, HI, USA

Date: 4/26/2019

Time: 11:00 AM

Room: Puget Sound

Following the Mw 6.9 Hawaiian earthquake on May 4, 2018 and the decay of its aftershock sequence, a remarkable quasi-periodic 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 June 4, 2018 through August 2, 2018 the collapse events, each releasing the energy equivalent of a Mw 5.3 ± 0.1 earthquake, occurred every 1.30 ± 0.32 days. This study focuses on the smaller seismicity (magnitudes ≥ 2.5, based on the fit of the data to Gutenberg-Richter scaling) occurring between collapse events at the summit. Between sequential pairs of collapses, the same temporal pattern of seismicity occurred. Following a large collapse event, there was a relatively quiescent period typically lasting 0.53 +/- 0.16 days. Following this quiescent period, there was a sudden onset of seismicity at a nearly constant rate of 397 +/- 96 earthquakes per day. These seismically active periods, lasting 0.77 +/- 0.33 days, with linear rates of seismicity, lasted until the next collapse event occurred. The temporal pattern then repeated itself beginning again with post-collapse quiescence. The pattern occurred 46 times between the 47 collapse events in our study period. A large shift in the rates of seismicity during the active times occurred around June 15th. There were also significant changes in the lengths of the quiescent times and the number of earthquakes during the total inter-event times that occurred around this date. Building on our preliminary study we are further investigating these trends and changes in the behavior of the smaller seismicity. Further statistical breakdown of the quiescent time behavior compared to the active time may give insight to the pre- and post-collapse volcanic and tectonic dynamics through-out the sequence.

Presenting Author: Rebecca A. Fildes

Authors