11:00 AM - 1:00 PM
[SVC31-P05] Local displacement at Mt.Esan detected by TS-InSAR
Keywords:SAR Interferometry, Esan, landslide, timeseries analysis
Introduction
Esan volcano, located at the southeastern end of Oshima peninsula, is one of the target volcanoes of JMA’s continuous monitoring. Two phreatic eruptions – in 1846 and in 1874 – is recorded in history (4th edition of National Catalogue of the Active Volcanoes in Japan). In recent years, fumarolic and seismic activities are observed at Esan volcano, however their activity level is low and the volcano is regarded as “calm”. Annual GNSS campaign observation carried out by Sapporo Regional Headquater, JMA shows small baseline extension since 2005.
On the other hand, numerous landslides and sediment disaster prone areas are recognized in this area. Even though no landslide is detected in the summit/crater basin, Murakami (2019) reported possible landslides at both western and eastern slope of the summit dome.
To investigate the detail of these local deformation and their time evolution, we applied SAR time-series analysis using ALOS-2/PALSAR-2 data.
Data and Method
We composed 45 interferometric pairs of path 18 (Descending, Right-looking), path 123 (Ascending, Right-looking) and path 124 (Ascending, Right-looking) observed by ALOS-2/PALSAR-2. We excluded observations in winter season to avoid incoherent interferograms which may lower the quality of the timeseries. We applied NSBAS method to those pairs using GIAnT (Agram et al., 2012) to detect time evolution of the deformation.
Result
The result timeseries of path 123 and path 124 shows line-of-sight distance increase at the summit region. The displacement rate increases in 2016, then stays constant until the latest observation, yielding total displacement of 14cm (path 124). This result agrees with GNSS campaign observation, which shows eastward and subsiding displacement at the station at the summit. On the contrary, path 18 result shows no obvious displacement at the same region. This is due to the fact that Line-of-Sight (LoS) direction of path 18 observation is almost perpendicular to the displacement direction.
As reported in Murakami (2019), path 18 shows deformation pattern at western slope of the summit. Unlike summit region, LoS distance change is increase or decrease depending on the period. This cannot be explained by pure landslide.
Acknowledgement
PALSAR-2 SLC data are provided by Japan Aerospace Exploration Agency (JAXA) via Coordinating Committee for the Prediction of Volcanic Eruption as part of the project ‘ALOS-2 Domestic Demonstration on Disaster management Application’. For interferogram processing, we used RINC (Ozawa et al., 2016) and Digital Ellipsoidal Height Model generated from Fundamental Geospatial Data (Elevation) published by GSI and EGM96 geoid (Lemoine et al., 1997). We used GSI tile for displaying displacement map.
Esan volcano, located at the southeastern end of Oshima peninsula, is one of the target volcanoes of JMA’s continuous monitoring. Two phreatic eruptions – in 1846 and in 1874 – is recorded in history (4th edition of National Catalogue of the Active Volcanoes in Japan). In recent years, fumarolic and seismic activities are observed at Esan volcano, however their activity level is low and the volcano is regarded as “calm”. Annual GNSS campaign observation carried out by Sapporo Regional Headquater, JMA shows small baseline extension since 2005.
On the other hand, numerous landslides and sediment disaster prone areas are recognized in this area. Even though no landslide is detected in the summit/crater basin, Murakami (2019) reported possible landslides at both western and eastern slope of the summit dome.
To investigate the detail of these local deformation and their time evolution, we applied SAR time-series analysis using ALOS-2/PALSAR-2 data.
Data and Method
We composed 45 interferometric pairs of path 18 (Descending, Right-looking), path 123 (Ascending, Right-looking) and path 124 (Ascending, Right-looking) observed by ALOS-2/PALSAR-2. We excluded observations in winter season to avoid incoherent interferograms which may lower the quality of the timeseries. We applied NSBAS method to those pairs using GIAnT (Agram et al., 2012) to detect time evolution of the deformation.
Result
The result timeseries of path 123 and path 124 shows line-of-sight distance increase at the summit region. The displacement rate increases in 2016, then stays constant until the latest observation, yielding total displacement of 14cm (path 124). This result agrees with GNSS campaign observation, which shows eastward and subsiding displacement at the station at the summit. On the contrary, path 18 result shows no obvious displacement at the same region. This is due to the fact that Line-of-Sight (LoS) direction of path 18 observation is almost perpendicular to the displacement direction.
As reported in Murakami (2019), path 18 shows deformation pattern at western slope of the summit. Unlike summit region, LoS distance change is increase or decrease depending on the period. This cannot be explained by pure landslide.
Acknowledgement
PALSAR-2 SLC data are provided by Japan Aerospace Exploration Agency (JAXA) via Coordinating Committee for the Prediction of Volcanic Eruption as part of the project ‘ALOS-2 Domestic Demonstration on Disaster management Application’. For interferogram processing, we used RINC (Ozawa et al., 2016) and Digital Ellipsoidal Height Model generated from Fundamental Geospatial Data (Elevation) published by GSI and EGM96 geoid (Lemoine et al., 1997). We used GSI tile for displaying displacement map.