Deformation of Mauna Loa before, during, and after its 2022 eruption

Mauna Loa on the Island of Hawaiʻi erupted on 27 November 2022, the first eruption since 1984, which marked the culmination of decades-long period of non-eruptive unrest and relative quiescence. We briefly describe the evolution of the USGS Hawaiian Volcano Observatory’s geodetic monitoring network at Mauna Loa and show patterns of deformation as measured by Global Navigation Satellite Systems (GNSS), interferometric synthetic aperture radar (InSAR), and borehole tilt. We highlight the long-term buildup and the imminent pre-eruptive geodetic signals, including subtle changes observed in early 2021 that suggested a potential eruption. We then describe the significant ramp up of activity in September 2022 that provided strong evidence of likely impending eruptive activity. Of particular importance are the first borehole tilt excursions related to magma movement measured at Mauna Loa’s summit, which began in 2021 and were accompanied by increased rates of seismicity. In addition to describing the evolution of surface displacements, we also model the co-eruption deformation, which can be fit by dike-like opening that matches the geometry of the surface eruptive fissures.