Migration of mechanical perturbations estimated by seismic coda wave
interferometry during the 2018 pre-eruptive period at Kīlauea volcano,
Hawaii
Abstract
We use seismic ambient noise correlation and coda wave interferometry to
estimate velocity variations at high temporal resolution, during the
pre-eruptive period and the onset of the 2018 eruption of Kilauea
volcano. A progressive velocity increase is observed from March to the
end of April. It is followed by rapid decrease starting a few days
before the onset of the East Rift Zone (ERZ) eruption and then by sharp
velocity drop when the eruption started. The change of trend from
velocity increase to decrease is progressively delayed by a few days
from the summit caldera toward the ERZ. The location of the velocity
perturbations shows a migration of the sources of velocity changes from
the summit caldera toward the ERZ before the eruption. Using a model of
pressure source, we show that the simultaneous caldera inflation and
velocity increase probably result from an anisotropic distribution of
fault and crack orientations. The velocity decrease could be due to
damaging processes above the shallow reservoir and to plastic
deformations around the caldera. We introduce a forward model of rock
damage associated with the volcano-tectonic seismicity to calculate the
velocity decrease. The good agreement between the calculated and the
observed velocity variations shows that a large part of the velocity
decrease results from damage of the medium. The delayed onsets of
velocity decrease and the source migration of velocity perturbations are
probably related to progressive fault openings in the Southern and
Eastern parts of the caldera and to magma transfer toward the ERZ.