Post Eruption Long Range Displacement Ground Deformation Monitoring of Large Rock Fractures at Hawaiʻi Volcanoes National Park

Abstract:

The East Rift Zone of Kīlauea Volcano experienced its largest eruption in nearly 200 years in 2018. Within Hawaiʻi Volcanoes National Park (HAVO), the eruption caused large-scale caldera collapse and has created ground instability in the summit area of Kīlauea Volcano. Areas impacted along Crater Rim Drive include the Jaggar Museum and Hawaiian Volcano Observatory facilities, along with associated roads and parking lots. The dramatic Halema'uma'u crater collapse removed approximately 500 m of buttressing rock from adjacent caldera faults. Significant park facilities near these faults along the northeast rim of the crater remain closed. The crater collapse occurred from May to early August of 2018 in 62 collapse events with thousands of shallow magnitude 2.5 or greater earthquakes also recorded in the summit area of Kīlauea Volcano. Lidar flown in July 2019 shows considerable changes to caldera cliffs, including significant rockfall since the July 2018 lidar collection.

To address concerns about ongoing ground deformation, long-range vibrating wire displacement meters were installed across caldera fault fracture zones in proximity to roads, trails, and buildings with associated damage from the 2018 crater collapse. Lidar indicates that these fracture zones vary from 20 to 40 m wide, expressed as near vertical faults at the surface. The instruments continuously monitor block and fault fracture movement. In order to adhere to park requirements of preserving the viewshed and minimizing impacts to the environment, the approximately 33 m long tensioned displacement meter cables were not encased in protective shielding, introducing wind noise into data collection. Ongoing seismicity will be detected if there is a resulting change in geometry between the instrumentation end points. However, the ground movement will only be detected if it is greater than noise from wind and thermoelastic expansion.

This project primarily seeks to monitor long-term ground deformation with short-term goals to address wind noise and thermal elastic expansion of instrumentation and rock. We aim to provide the National Park with quality data that will inform decisions regarding policies following felt earthquakes, facilities operations, and reopening the area and facilities for future public visitation.