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

Surface deformation associated with the 2018 Mw 6.9 earthquake off the coast of the Hawai'i island. (a) Map view of Kīlauea's south flank and normal fault systems (KSC = Kīlauea summit caldera; ERZ = East Rift Zone; KFS=Koa'e fault system; HFS=Hilina fault system). The gray and red stars represent the epicenters of the 1975 M7.7 Kalapana and 4 May 2018, M 6.9 earthquake, respectively. The black lines with black text labels denote the active fault traces mapped by U.S. Geological Survey (USGS; Cannon et al., 2007). KP= Kulanaokuaiki Pali; PoP=Poliokeawe Pali; HP=Hōlei Pali; AP='Āpua pali; PP=Palama pali; PS=Paliliu section. The thick blue and red line segments show the approxi- mate extent of the intrusions associated with the 2007 Father's Day and 2011 Kamoamoa eruptive events along the ERZ. The background color shows the mean line‐of‐sight (LOS) displacements due to the 2018 Kīlauea eruption‐earthquake sequence derived from the stack of descending COSMO‐Skymed (CSK, track D165) interferograms spanning the 2018 earthquake. (b) Line‐of‐sight (LOS) displacements across the KFS derived from COSMO‐Skymed (CSK) data from descending track D165. (c) Line‐of‐sight (LOS) displacements across the Poliokeawe and Hōlei Palis derived from COSMO‐Skymed data of the ascending track A10.

Project Summary 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.

Tools GPS and InSAR

Geographic Location Kīlauea, Hawaii

Group Members Involved Kang Wang <Email> <Personal Web Site> Ingrid Johanson, Eric Cannon, Matt d'Alessio, Roland Bürgmann

Project Duration 2018 - 2019

More Information JGR article < Wang et al., 2019 >