Top‐down inflation and deflation at the summit of Kīlauea Volcano, Hawai‘i observed with InSAR

We use interferometric synthetic aperture radar (InSAR) to study deformation of the summit caldera at Kīlauea Volcano during 2000–2008, which spanned both an east rift zone eruptive event in 2007 and the start of the ongoing summit eruption in 2008. The data set consists of small baseline subset (SBAS) time series generated from 270 acquisitions on three separate beam modes from the Radarsat‐1 satellite. We identify 12 time periods with distinct patterns of displacement that we attribute until late 2003 to secular tectonic‐driven deformation and from 2004 to 2008 to four different sources in the summit area. We model the shallow magmatic system as a spherical reservoir at 1.9 ± 0.1 km depth below the surface to the northeast of Halemaumau (source 1) and three vertically stacked sills at greater depths in the southern caldera area (source 2 at the southern edge of the caldera at 2.9 ± 0.2 km depth, source 3 to the south‐southeast of the caldera at 3.4 ± 0.5 km depth, and source 4 south of the caldera at 3.6 ± 0.4 km depth). The sequence for filling of and withdrawal from these reservoirs reveals a top‐down process, with sequences of both inflation and deflation initiating in the shallowest source. Inflation of source 3 is coincident with elevated seismic activity in the upper east rift zone in February 2006 and May 2007. Source 4 is elongated toward the southwest rift zone and also shows elevated seismicity that extends toward the southwest rift zone.