Mapping Vertical Land Movement in Singapore Using Insar and Gps

In this study we investigate the spatial variation in vertical land motion (VLM) along the coast of Singapore over the past two decades and we examine the impact of spatially variable VLM on relative sea level trends. For that, we use an integrated approach based on the merging of terrain displacement velocities estimated by time series of interferometric synthetic aperture radar (InSAR) data acquired along ascending and descending orbits and repeated GPS measurements. We processed 39 single look complex images from ERS2 satellite (ascending and descending passes) spanning from October 1995 until January 2000. The vertical velocities of 5 continuous GPS stations of the Singapore Satellite Positioning Reference Network (SiReNT) were used as constraints in the PS solutions to further enhance the solution quality. The results show that Singapore mainland has experienced subsidence phenomena from 1995 to 2000 with a mean subsidence rate of -1.5 mm/yr. On some localized areas, a significant subsidence with rates of -7 mm/yr was detected. Highest subsiding rates are near the shore on low flat land, above 5m, associated with reclaimed areas or built areas in the past years. The result seems to be reliable and consistent with the geologic setting. The scatter pattern of the deformation indicates anthropogenic causes, related with compaction of built and/or reclaimed areas, rather than natural causes.