Land subsidence analysis in Surabaya urban area using time series InSAR method

Surabaya's geological condition that dominated by alluvium unconsolidated, as well as increasing growth of buildings-especially skyscrapers-are triggered the surface deformation on the area. This research aims to monitor and analyze the surface deformation, especially the subsidence that occurred in Surabaya urban area over the last two years. We use Remote Sensing Technology that has been widely developed, not only aims to observe and analyze objects on the earth, but also very useful to monitor land surface changes. Interferometric Synthetic Aperture Radar (InSAR) is the first known technique to get surface deformation measurement effectively on large areas (thousands of km²) up to sub-centimeters. However, the technique also has limitations. In order to overcome the limitations of InSAR, multi-temporal InSAR techniques have been recently developed and one of them is Small Baseline Subset (SBAS). This time-series technique tries to overcome the temporal decorrelation due to atmosphere effect and measure transient movement on the Earth surface by using multi-look interferograms combination and small baseline temporal selection. Using SBAS technique we processed 24 Sentinel-1A images from Mei 2015 to Mei 2017 and 28 Sentinel-1A images from May 2015 to September 2017 to extract information of vertical displacement in Surabaya and compare both of them. The result shows that during the observation period, the rate of deformation in the form of Line of Sight Displacement (LOS) is varies from -60mm/year to +20mm/year. The majority of subsidence occured in coastal area (Northern and Eastern part) whereas the majority of uplift occured in the Surabaya downtown area (Southern and Western part).