Volcanic eruptions are potentially hazardous natural events.
Understanding how magma accumulates, migrates, and erupts is important
to understanding and, eventually, predicting volcanic eruptions.
However, the variation in the scale of volcanoes, co-occurrence of
earthquakes, and the duration of the eruption makes understanding these
events difficult. Ambient noise interferometry is becoming an
increasingly more popular tool to study and monitor active volcanoes. We
use this method to characterize the variations of subsurface seismic
velocities associated with different stages of the eruption process at
the Great Sitkin Volcano in the central Aleutian volcanic arc. This
volcano initially erupted in May 2021 with elevated seismicity and gas
release, followed by the formation of a new lava dome starting July
2021. The volcano had an increase in seismicity in February 2020 but
without any eruption activity reported. Measuring the variation of
seismic velocities from August 2019 to March 2022, we observe a local
decrease in velocity leading up to the eruption and an increase in
velocity following the emplacement of the lava dome. We do not observe
any velocity variations preceding the non-eruptive increase of seismic
activity in February 2020. Despite its remote location and relatively
small scale, the findings of this study at the Great Sitkin volcano have
significant implications for understanding volcanism and the development
and prediction of volcanic eruptions in general.