[S-TT36] Synthetic Aperture Radar and its application

[STT36-P02] Surface displacement in Hachijojima Island since 2014 by InSAR analysis and GNSS

*yusei Hamamura¹, HIROYUKI AZUMA¹, Yoshiya Oda¹ (1.Tokyo Metropolitan University)

In this study, as a volcanic disaster prevention study, the surface displacement of Hachijojima Island, a volcanic island belonging to Tokyo Metropolitan, has been estimated by InSAR time series analysis, ALOS-2 PALSAR-2 data observed during the period from August 2014 to August 2020 are used for InSAR analysis. In this study, we employed SBAS(Small Baseline Subset) method, which in one of the methods for InSAR time series analysis. 83 pairs for Descending, and 26 pairs for Ascending are used for SBAS analysis. In addition, we analyzed GNSS data observed at JMA “South mountainside of Nishiyama” station to verify the results.
The results of InSAR analysis, it is not possible to confirm significant displacement above noise level. In addition, it was not possible to find the long-term sueface displacement trend.
The results obtained by InSAR time series analysis are described. On Hachijojima Island, no regions with surface displacement of 4 cm or more was observed in 6 years. But it was confirmed that analysis results of both Descending and Ascending showed uplifting surface displacement in the flat area between Nishiyama and Higashiyama and near the summit of Nishiyama. Specifically, a displacement of about 4 cm was confirmed on the flat land, and a displacement of about 2 cm was confirmed near the summit of Nishiyama. Those area correspond to the area of the lavas of the Senjojiki stage and Okoshigahana Scoria fall.