The lower East Rift Zone intrusion at Kīlauea Volcano, 2018 from GPS, InSAR and tilt

Abstract:

The lower East Rift Zone eruption that occurred during the 2018 eruptive sequence at Kīlauea Volcano, Hawaii, began with internal migration of magma from the previous middle east rift zone eruption site at Pu`u `Ō`ō down to the lower rift zone about 20 km downrift. GNSS and InSAR data indicated up to ~2 m of displacement. Geodetic modeling for the geophysical eruption response during the early phases of the eruption indicated a single dike structure that grew and expanded in several phases. These models indicated that 90x10⁶ m³ of new magma injected into the rift zone, which is only about 10% of the volume erupted (estimated at 900–1500x10⁶ m³), and the volume withdrawn from the summit caldera (~825x10⁶ m³), although these estimates are still preliminary. The dike orientation was relatively well constrained, striking roughly 62^o and parallel with the surface trace of the rift zone, as was the amount of opening at about 4 m. The easternmost dike tip did not extend beyond the farthest eruptive fissure. A portion of the dike intruded uprift of the eruptive fissures, a feature commonly observed during previous intrusions at Kīlauea. Other geometrical parameters, however, were not as well constrained including the dip of the dike and its bottom depth. Deformation models also indicate a substantial amount of magma was withdrawn from the plumbing and reservoirs uprift along the middle east rift zone, potentially contributing an additional 45–50x10⁶ m³ of magma to the eruption that may not have been immediately derived from the summit reservoir. A number of factors influence the data from Kīlauea’s lower east rift zone, and are important to consider when modeling this intrusion. Data limitations include substantial forest cover complicating radar interferograms, sparse continuous ground-based near-field geodetic data, and additional geologic events (e.g., a M6.9 earthquake, summit collapse, and extensive lava flows) that complicated the modeling of the dike. It is critical to consider with the underlying geology and structures at Kīlauea, as well as all of the events that transpired during the 2018 eruptive sequence, to properly interpret and model the deformation.