Summit and rift vent progression captured by infrasound during the 2022 Mauna Loa eruption

The 2022 Mauna Loa eruption began on November 27 23:21 HST (November 28 9:21 UTC) at the summit, based on the onset of seismic tremor and visual observations of nighttime incandescence from lava viewed by webcameras.  Continued visual observations noted early southwestward migration of the summit flows followed by dike propagation and new fissures on the northeast rift zone in the early hours of November 28^th HST.   Northeast rift zone activity subsequently settled into persistent activity primarily from Fissure 3 (located about 7 km from the Summit) until the eruption stagnated by December 9^th HST.

This contribution provides a detailed retrospective assessment of the performance of four Hawaiian Volcano Observatory (HVO) infrasound arrays (AIND, AHUD, MENE, SHEEP) and an International Monitoring System array operated by the University of Hawaii Infrasound (I59US) data during the onset and progression of the eruption.  We use results from a standard least-squares beamforming algorithm which is widely used for infrasound processing across the USGS Volcano Science Center and compare other multidisciplinary observations such as visual and seismic amplitude.

We find that that the standard array processing approach performed adequately as a real-time assessment tool with high correlation back-azimuth computations in reasonable agreement with visual observations.  High winds associated with storms impacted the quality of our results, particularly toward the end of the eruption when infrasound signals were comparably small.  It was possible to distinguish between summit and rift fissure activity using the three long-term arrays operated by HVO, despite the large source to receiver distance.  The SHEEP array (on the south flank of Mauna Kea) was established in response to the Mauna Loa eruption and only recorded the waning phase of the eruption.  Regardless, the new array should further improve azimuthal coverage for future Mauna Loa eruptive activity.