3:30 PM - 3:45 PM
[HDS08-06] Detection of Reclaimed Valley Deformations by InSAR Time Series Analysis and GNSS Observation
Keywords:Reclaimed valleys, Landslides, InSAR time series analysis, GNSS observation
In Japan, beginning with the urbanization starting in the 1960s, a lot of valleys were reclaimed to use as residential estates. Recent earthquakes, such as the 2011 Mw 9.0 Tohoku-Oki Earthquake, the 2016 Mw 7.0 Kumamoto Earthquake, and the 2018 Mw 6.6 Hokkaido Eastern Iburi Earthquake, have triggered landslides in gentle slopes in reclaimed valleys and resulted in severe damage to housing lots. There is a high possibility that will happen again in the future, so it is very important to evaluate and monitor the health of the reclaimed valleys and take measures as necessary. We detected reclaimed valley deformation in Sendai city occurred during the 11 March 2011 Tohoku-Oki Earthquake by InSAR analysis and examined its usability (Miyajima et al., 2022). Phase changes were observed where actual damages had been reported, which indicated the validity and usability of InSAR on detecting reclaimed valley deformation. Moreover, we detected small displacements away from the satellite on some reclaimed valleys where no damage to housing lots had been reported. In this study, we place GNSS receiver in public facilities built in reclaimed valleys and compare the results of InSAR and GNSS analysis to verify the reliability of the signals detected by InSAR.
We conduct three studies: 1) InSAR time series analysis, 2) GNSS observation, and 3) comparison between the results of InSAR and GNSS analysis. As a result of InSAR analysis using ALOS2/PALSAR2 data, we detected small displacements away from the satellite in some residential districts including Yagiyama, Midorigaoka, and Yakata districts, during the Earthquake off the Coast of Fukushima Prefecture in February 2021 and March 2022. On the contrary, in residential districts in the Nanakita River Basin, where distinct phase changes were observed during the 2011 Tohoku-Oki Earthquake, no displacements were detected. These results suggest that there is a variety in the responses against strong shakings in different reclaimed valleys. We also present our situation in GNSS observations and InSAR time series analysis using the StaMPS software (Hooper, 2008).
We conduct three studies: 1) InSAR time series analysis, 2) GNSS observation, and 3) comparison between the results of InSAR and GNSS analysis. As a result of InSAR analysis using ALOS2/PALSAR2 data, we detected small displacements away from the satellite in some residential districts including Yagiyama, Midorigaoka, and Yakata districts, during the Earthquake off the Coast of Fukushima Prefecture in February 2021 and March 2022. On the contrary, in residential districts in the Nanakita River Basin, where distinct phase changes were observed during the 2011 Tohoku-Oki Earthquake, no displacements were detected. These results suggest that there is a variety in the responses against strong shakings in different reclaimed valleys. We also present our situation in GNSS observations and InSAR time series analysis using the StaMPS software (Hooper, 2008).