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A sequence of eruptions in the lower East Rift Zone (LERZ) of the Kilauea, Hawaii volcano commenced in early May 2018 and caused serious damage and residential evacuation. The post-eruption drainage and collapses of the summit lava lake and caldera suggest a well-connected magmatic plumbing system along the rift zone. How and when the pre-eruptive magmatic processes in such connecting system occurred are, however, still unclear. For that, we apply ambient noise interferometry with seismic data from January 2017 to June 2018 from 12 broadband seismometers to investigate spatiotemporal seismic velocity changes (dv/v) of the upper crust in the Kilauea area. The dv/v variations in three frequency bands (0.3–0.6 Hz, 0.6–0.9 Hz, and 0.9–2.0 Hz) show distinct responses to strong earthquake ground shaking and deep magmatic intrusion processes. Earthquake-induced dv/v drops mainly in the higher two frequency bands imply shallow mechanical changes within the uppermost 1 km of the crust. In contrast, the magma-related dv/v changes can be characterized into three periods of activity: from the December 2017 to March 15, 2018, a dv/v excursion only seen in the lowest frequency band indicates the magmatic intrusion processes taking place at the depth range of 1–4 km, consistent with the proposed depth of the magma reservoir-dike system in the rift zone. The spatial dv/v distribution suggests that the magma may intrude to the deeper summit magma reservoir and in the upper East Rift Zone (UERZ) at this time. From March 15 to April 17 in 2018, the summit inflation recorded by tiltmeters causes the dv/v increases in the higher two frequency bands. After April 17 to the eruption, the accumulating damage of the edifice together with the stronger intrusion activity in the UERZ result in dv/v decreases in all three frequency bands around the summit and UERZ areas. Our observations highlight that the ambient noise interferometry analysis provides an opportunity to image and understand the pre-eruptive processes of reservoir-dike magma system and could be a useful supplement to current volcanic monitoring systems. [ABSTRACT FROM AUTHOR]

A sequence of eruptions of the Kilauea volcano, Hawaii commenced in early May 2018 and caused serious damage and residential evacuation. To understand the magma intrusion process, which produces little measurable effect at the surface prior to the eruption, we use seismic noise interferometry and ~1.5-year vertical-component seismic data from 6 broadband seismometers to investigate temporal seismic velocity changes (dv/v) at depth near Kilauea. Analyses of three different frequency bands (0.3-0.6 Hz, 0.6-0.9 Hz, and 0.9-2.0 Hz) show distinct earthquake-related and magma-related structural changes in the uppermost 500 m and below 1 km from the surface. The magma-related dv/v began in December 2017 and exhibit a dichotomous pattern of seismic velocity that increases to the southwest and slightly decreases to the northeast of the East Rift Zone, revealing an intrusive magma process with a long precursory phase beginning almost a half year before the May 2018 eruption. [ABSTRACT FROM AUTHOR]