ANALYSIS OF THE TREND OF THE DEFORMATION AROUND KANTO REGION ESTIMATED BY TIME SERIES OF PALSAR-2 DATA

Abstract. The South Kanto gas field contains natural gas dissolved in water. In the past, large-scale land subsidence has occurred due to the extraction of this natural gas. Therefore, continuous and accurate monitoring for subsidence using satellite remote sensing is essential to prevent any extreme subsidence events, particularly in urban areas, and ensure the safety of residences. In this study, we adopted the small baseline subset (SBAS) method to understand the subsidence trend. We used Advanced Land Observing Satellite (ALOS)-2 Phased Array type L-band Synthetic Aperture Radar (PALSAR-2) data from 2015 to 2019 for this purpose. The results show that the maximum displacement around the Kujyukuri area is more than 10 mm/year and the mean displacement rate for 2015 to 2019 is -1.4 ± 3.2 mm/year; this value is not as large as some obtained with past PALSAR observations. Comparison of our results with PALSAR observations shows that the number of distributed targets is fewer and the root mean square error of each time-series displacement value is larger. Further quantitative analysis is required to discuss the reliability of the SBAS-derived displacement rates by PALSAR-2.