17:15 〜 18:45
[STT35-P05] Estimation of Ground Motions in Chiba Prefecture Using ALOS-2 PALSAR-2 Data
キーワード：だいち２号、地盤変位、干渉SAR時系列解析
Recently, ground deformation caused by groundwater pumping and natural gas extraction has become a problem in Chiba Prefecture. Therefore, mid- to long-term monitoring of ground deformation is essential for disaster prevention and mitigation of damage caused by ground deformation. Currently in Japan, monitoring is conducted using the method of leveling, which requires a large amount of manpower and time. On the other hand, satellite remote sensing enables wide-area observations, and many studies have been conducted on monitoring ground deformation using synthetic aperture radar (SAR). In previous studies, C-band sentinel-1 was used to estimate the displacement in Chiba Prefecture. This study aims to evaluate the ground displacement in Chiba Prefecture by utilizing L-band PALSAR-2 data on ALOS-2, and to gain knowledge on its characteristics.
To estimate the ground displacement, differential interferometory synthetic aperture radar (DInSAR) is often performed. However, spatial and temporal decorrelation severely restrict the use of DInSAR, especially for long-term time-series monitoring of urban areas. The small baseline subset (SBAS) technique is an extension of conventional DInSAR method. In this study, we used 32 images taken approximately every 3 months, from January 2015 to October 2023.
The displacement velocities using the ALOS-2 data for Chiba Prefecture were obtained and compared with the land cover map and GNSS Earth Observation Network System (GEONET) data. Compared to the land cover map, it can be seen that the displacement velocity can be estimated for the urban area in the northwest, while it is not available for the mountainous area in the south. The ground displacement exceeding about 15 mm/year was observed in Yachimata and Tomisato City, while 10 mm/year in Mobara City and Chosei-gun. Comparing the displacement velocity in the line-of-sight direction estimated by ALOS-2 with the GEONET data, ALOS-2 captured the trend of displacement, although offsets were observed. Only for the Hanamigawa, the trend was different because spike-like displacement was observed at the GEONET data.
To estimate the ground displacement, differential interferometory synthetic aperture radar (DInSAR) is often performed. However, spatial and temporal decorrelation severely restrict the use of DInSAR, especially for long-term time-series monitoring of urban areas. The small baseline subset (SBAS) technique is an extension of conventional DInSAR method. In this study, we used 32 images taken approximately every 3 months, from January 2015 to October 2023.
The displacement velocities using the ALOS-2 data for Chiba Prefecture were obtained and compared with the land cover map and GNSS Earth Observation Network System (GEONET) data. Compared to the land cover map, it can be seen that the displacement velocity can be estimated for the urban area in the northwest, while it is not available for the mountainous area in the south. The ground displacement exceeding about 15 mm/year was observed in Yachimata and Tomisato City, while 10 mm/year in Mobara City and Chosei-gun. Comparing the displacement velocity in the line-of-sight direction estimated by ALOS-2 with the GEONET data, ALOS-2 captured the trend of displacement, although offsets were observed. Only for the Hanamigawa, the trend was different because spike-like displacement was observed at the GEONET data.