5:15 PM - 6:30 PM
[SVC28-P01] Local deformation at Mt.Tokachi detected by TS-InSAR
Keywords:Mt.Tokachi, SAR Interferometry, Crustal Deformation
Introduction
Mt.Tokachi is one of the most active volcanoes in Hokkaido, Japan. Its notable eruptions took place around every 30 years; in 1926, 1962 and 1988-89 (4th edition of National Catalogue of the Active Volcanoes in Japan). 32 years have passed since the last eruption, which implies that Mt.Tokachi is at a preparation stage for the next eruption.
GNSS observation revealed the local inflation since 2006, and as much as 10cm of displacement is observed at Mae-Tokachi GNSS station established by Geological Survey of Hokkaido. After that, inflation slowdowned in 2017, then turned to deflation in 2018.
We have been monitoring the activity of Mt.Tokachi through SAR interferometry and reported about the deformation at western flank (Okuyama et al., 2019). In this presentation, we report the result of time-series analysis using GIAnT (Agram et al., 2012).
Data and Method
We composed 58 pairs of path 122 (Ascending, Right-looking), path 17 (Descending, Right-looking) and path 18 (Descending, Right-looking) observed by ALOS-2/PALSAR-2. We could not collect large number of SAR images due to low observation frequency and the fact that the target area is covered by snow for more than 6 months. Hence, to increase the number of pairs, we regard path 17 and 18, whose incidence angles differ by about 10 decimal degrees, as same path of which incidence angle is the average of those. We applied NSBAS method to those pairs to detect time evolution of the deformation, linearly interpolated between observation dates, then calculated two-dimensional displacement.
Result
The result timeseries show two main characteristics – upheaval around Furikozawa fumaroles and complex deformation at the slope located at the west of Mae-Tokachi. The former turns into subsidence in late 2017, then became stagnant after 2018. This trend is same as the displacement observed at Mae-Tokachi GNSS station. The latter, on the other hand, shows partial correspondence with the topography, which implies the effect of landslide. However, as we reported in Okuyama et al. (2019), the pattern includes local upheaval, which cannot be explained by the landslide. Unlike the deformation around Furikozawa fumaroles, these deformation progress at a uniform rate.
Acknowledgement
PALSAR-2 SLC data are shared among PIXEL (PALSAR Interferometry Consortium to Study our Evolving Land surface), and provided from JAXA under a cooperative research contract with ERI, Univ., Tokyo. The ownership of PALSAR-2 data belongs to JAXA. We used RINC (Ozawa et al., 2016) and Fundamental Geospatial Data (Elevation) published by GSI for interferogram processing. We used GSI tile for displaying displacement map.
Mt.Tokachi is one of the most active volcanoes in Hokkaido, Japan. Its notable eruptions took place around every 30 years; in 1926, 1962 and 1988-89 (4th edition of National Catalogue of the Active Volcanoes in Japan). 32 years have passed since the last eruption, which implies that Mt.Tokachi is at a preparation stage for the next eruption.
GNSS observation revealed the local inflation since 2006, and as much as 10cm of displacement is observed at Mae-Tokachi GNSS station established by Geological Survey of Hokkaido. After that, inflation slowdowned in 2017, then turned to deflation in 2018.
We have been monitoring the activity of Mt.Tokachi through SAR interferometry and reported about the deformation at western flank (Okuyama et al., 2019). In this presentation, we report the result of time-series analysis using GIAnT (Agram et al., 2012).
Data and Method
We composed 58 pairs of path 122 (Ascending, Right-looking), path 17 (Descending, Right-looking) and path 18 (Descending, Right-looking) observed by ALOS-2/PALSAR-2. We could not collect large number of SAR images due to low observation frequency and the fact that the target area is covered by snow for more than 6 months. Hence, to increase the number of pairs, we regard path 17 and 18, whose incidence angles differ by about 10 decimal degrees, as same path of which incidence angle is the average of those. We applied NSBAS method to those pairs to detect time evolution of the deformation, linearly interpolated between observation dates, then calculated two-dimensional displacement.
Result
The result timeseries show two main characteristics – upheaval around Furikozawa fumaroles and complex deformation at the slope located at the west of Mae-Tokachi. The former turns into subsidence in late 2017, then became stagnant after 2018. This trend is same as the displacement observed at Mae-Tokachi GNSS station. The latter, on the other hand, shows partial correspondence with the topography, which implies the effect of landslide. However, as we reported in Okuyama et al. (2019), the pattern includes local upheaval, which cannot be explained by the landslide. Unlike the deformation around Furikozawa fumaroles, these deformation progress at a uniform rate.
Acknowledgement
PALSAR-2 SLC data are shared among PIXEL (PALSAR Interferometry Consortium to Study our Evolving Land surface), and provided from JAXA under a cooperative research contract with ERI, Univ., Tokyo. The ownership of PALSAR-2 data belongs to JAXA. We used RINC (Ozawa et al., 2016) and Fundamental Geospatial Data (Elevation) published by GSI for interferogram processing. We used GSI tile for displaying displacement map.