Observing posteruptive deflation of hydrothermal system using InSAR time
series analysis: An application of ALOS-2/PALSAR-2 data on the 2015
phreatic eruption of Hakone volcano, Japan
Abstract
From 29 June to 1 July, 2015, a phreatic eruption occurred in Owakudani,
the largest fumarole area in Hakone volcano, Japan. In this study, an
interferometric synthetic aperture radar (InSAR) time series analysis of
the Advanced Land Observing Satellite-2 (ALOS-2)/Phased Array type
L-band Synthetic Aperture Radar-2 (PALSAR-2) data was performed to
measure deformation after the eruption. The results show that the
central cones of the volcano have subsided since the eruption and its
deflation source is located beneath the previously estimated bell-shaped
conductor, which is considered as a sealing layer confining a
pressurized hydrothermal reservoir. Therefore, the InSAR results
demonstrate the deflation of the hydrothermal system beneath the
volcano. One possible cause of this deflation is compaction due to a
decrease in pore pressure caused by rupture and fluid migration during
and after the eruption.