Bruce Thomas, James Foster

20 years of ground deformation patterns along Koa’e fault zone on Kīlauea volcano

Extreme long-term extensions are experienced along the Koa’e fault zone, a structural linkbetween the East Rift zone and the Southwest Rift Zone on Kīlauea volcano. Both tectonic motions of the south flank of the volcano, as well as magma storage and transport at the summit and along the rift zones create stresses and ground motion patterns across this fault zone. To assess the role of Koa’e structure in these processes, and its contribution to hazard potential, this study investigates 20 years of survey GNSS data along a benchmark line running from south of Kīlauea’s caldera through the Koa’e fault zone. This survey was realized by BruceThomas with the help of James Foster and Jon Avery (University of Hawai’i) in 2017, late 2021 and late 2022 (Figure 1). We would also like to acknowledge the contribution during this project of Andi Ellis and David Phillips from the Hawaiian Volcano Observatory, as well as the help given by the Hawai’i Volcanoes National Park.

Fieldwork in progress on Kīlauea volcano.

First results of the deformation data capture trends of inflation/deflation from the summit magma chambers during eruptive events, as well as transient local signals from both tectonic and magmatic processes, highlighting the complexity of the volcanotectonic processes active in and around the Koa’e fault zone. Mapping the cumulative displacement over the last 20 years captures the response to the constant southeast seaward slip of the south flank which results in earthquake swarms, open fractures, intrusion of magma through shallow paths and the possible risk of eruptive fissures. This dataset is being used to guide numerical models of the kinematic deformation of this area.

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