Surface Deformation Assessment due to the Grindulu Fault Activities using Sentinel 1 Data by Applying the Small Baseline Subset (SBAS)-InSAR Technique

The location of Grindulu Fault is in the Pacitan Regency on the Southern Coast of Java, which directly faces the South Java Subduction zone. The activities of the fault could contribute to the surface deformation in the surrounding area. The Meteorology Climatology and Geophysics Council in Indonesia (BMKG) reported a 3.1 Mw earthquake on 7 November 2019, possibly related to the Grindulu fault activities. In this research, we assess the surface deformation around the Grindulu Fault using the Sentinel I data by applying the Small Baseline Subset (SBAS) - Interferometry Synthetic Aperture Radar (InSAR) technique. The SBAS-InSAR is one of the techniques that can provide spatial-temporal continuous analysis of the surface deformation over the extent of InSAR data. The SBAS algorithm was applied to twenty-three (23) ascending Sentinel-1B images to assess the surface deformation in Pacitan between 2019 and 2021 using the GMTSAR software. The results showed surface deformation dominated by subsidence over the whole area, except at the northern part of Grindulu Fault, with the mean velocity values ranging from -2.07 to -43.05 mm/yr.