GEODETIC MONITORING OF 2021-2024 INTRUSIVE MAGMATIC EVENTS IN THE KOA’E FAULT SYSTEM OF KĪLAUEA VOLCANO, HAWAI’I

Near-surface deformation in the Koa’e fault system underpins our understanding of intrusive magmatic dike events of the Kīlauea volcano. The active Koa’e fault system lies south of the summit caldera and connects the Southwest Rift Zone (SWRZ) and East Rift Zone (ERZ) of Kīlauea along a series of east-northeast trending faults. Extensional structures in the Koa’e fault system result from seaward motion and detachment of Kīlauea’s south flank. Due to localized uplift and limited eruptions over the past ~500 – 700 years, the faults in the area remain uncovered, making them ideal to study. Repeated dike intrusions in the SWRZ and the ERZ push the south flank of Kīlauea more southerly, accelerating flank subsidence and thus representing a shear zone as this process occurs. In 2023, Kīlauea experienced three eruptions confined within Halema’uma’u caldera. Eruptions at the summit have been accompanied by several dike intrusions into the upper SW rift connector between 2021 and 2024. To track the intrusions, we used two geodetic monitoring techniques. To measure vertical displacement along each fault block, we used traditional high-accuracy line leveling techniques to reoccupy existing geodetic monuments originally established in the 1960s by USGS-Hawaiian Volcano Observatory staff. Additionally, we measured the inflation and deflation trends of the fault system using kinematic GPS over the same geodetic network and constructed three-dimensional point-cloud models of several faults in the system to set a baseline to detect change from future fault movements. Using these geodetic techniques, we measured up to 30 cm of uplift following the September 2023 eruption. By analyzing the uplift trends of the fault blocks, we hypothesize that individual faults within the Koa’e fault system govern the path of magma injection into the south caldera and upper Southwest rift connector.