Abstract
Mauna Loa volcano on the island of Hawaii is the world's largest active volcano. After 38 years of quiescence, an eruption began on November 27, 2022 HST in Mokuaweoweo, the summit caldera of Mauna Loa. The eruption continued at the summit and the Northeast Rift Zone and lasted 12 days. In this study, I investigate the spatial and temporal variations of seismicity distribution and subsurface velocity structure before and after this eruption. The seismic data, reviewed by the Hawaiian Volcano Observatory (HVO) analysts, are downloaded from the U.S. Geological Survey and the Incorporated Research Institutions for Seismology (IRIS). The initial locations, phase arrival times, and waveform data are acquired for over 7,500 earthquakes from September 1, 2015 to May 31, 2023. High-precision locations for these earthquakes are obtained by applying three-dimensional ray tracing through a previous velocity model and waveform cross-correlation location method. The location accuracies, especially in depth, of the shallow magma reservoir and the decollement are significantly improved compared to the initial HVO catalog. Daily continuous seismic data in 2022 are also downloaded from IRIS and autocorrelation of seismic noise is conducted to examine temporal seismic velocity variations before the eruption. Preliminary results at the summit seismic stations show a gradual velocity increase from July to mid-October, followed by a slow decrease for over a month and an abrupt increase right before the eruption.