Interseismic Quiescence and Triggered Slip of Active Normal Faults of Kīlauea Volcano's South Flank During 2001–2018

• Published in: Journal of geophysical research. Solid earth Vol. 124; no. 9; pp. 9780 - 9794
• Main Authors: Wang, K., MacArthur, H. S., Johanson, I., Montgomery‐Brown, E. K., Poland, M. P., Cannon, E. C., d'Alessio, M. A., Bürgmann, R.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-09-2019
• Subjects: Calderas; earthquake; Earthquakes; Fault lines; Faults; Geological faults; Geophysics; Global positioning systems; GPS; Hilina fault; InSAR; Interferometric synthetic aperture radar; Interferometry; Kīlauea Volcano; Lava; Magma; Positioning systems; Radar; Radar data; Rift zones; SAR (radar); Seismic activity; Seismic response; Slip; Subsidence; Synthetic aperture radar; Synthetic aperture radar interferometry; triggered slip; volcano; Volcanoes
• ISSN: 2169-9313; 2169-9356
• DOI: 10.1029/2019JB017419

The mobile south flank of Kīlauea Volcano hosts two normal fault systems, the Koa'e fault system (KFS) and the Hilina fault system (HFS). In historical time, at least three M>6.5 earthquakes have occurred on the basal detachment of the Kīlauea Volcano's south flank, with the most recent being the 4 May 2018 M6.9 earthquake. Here we analyze kinematic Global Positioning System data collected from 2001 to 2017 and interferometric synthetic aperture radar data before, during, and after the 2018 M6.9 earthquake to determine the crustal motion across the HFS and KFS faults. Our results indicate that the HFS faults did not significantly slip during the interseismic period from 2007 to 2011. Despite its substantial magnitude, interferometric synthetic aperture radar (InSAR) data show that the 2018 M6.9 earthquake triggered subcentimeter level slip along sections of the previously mapped HFS branches. Up to 20 cm of offset occurred on what appears to be a newly formed (or previously unknown) fault near the eastern end of the HFS. During the 3 months following the M6.9 earthquake, up to ~30 cm of slip occurred along the KFS, which helps accommodate rapid large‐scale subsidence of Kīlauea's summit region as large volumes of summit reservoir magma fed the lower East Rift Zone eruption. The HFS appears to activate only in concert with large earthquakes on the basal detachment. The KFS, on the other hand, moves both seismically during small local earthquakes and aseismically in response to nearby earthquakes and caldera subsidence.
Key Points
GPS data show no interseismic slip on Hilina fault system (HFS) during 2001–2017
InSAR shows subcentimeter HFS offsets in the 4 May 2018 M6.9 earthquake
A new fault scarp formed on eastern end of the HFS during and after the earthquake