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High nonlinear urban ground motion in Manila (Philippines) from 1993 to 2010 observed by DInSAR: Implications for sea-level measurement

Raucoules, Daniel, Le Cozannet, Gonéri, Wöppelmann, Guy, de Michele, Marcello, Gravelle, Médéric, Daag, Arturo, Marcos, Marta
Remote sensing of environment 2013 v.139 pp. 386-397
climate change, equipment, geodesy, global positioning systems, groundwater, image analysis, interferometry, remote sensing, sea level, subsidence, urban areas, Philippines
In coastal low-lying urban areas, vertical ground motions can significantly exacerbate the hazards related to sea-level rise. However, their spatial extent, their temporal evolution, and even sometimes their existence are often poorly known. This study aims to monitor variable urban ground motion (uplift and subsidence) from 1993 to 2010 in the metropolitan area of Manila, Philippines. Because high subsidence rates have been reported in this city in previous studies, conventional Differential SAR Interferometry (DInSAR) was applied with an adapted stacking procedure to the archive of ERS and Envisat satellite images to produce surface deformation-velocity maps for different periods. The results showed that the city is locally affected by vertical ground motions on the order of 15cm/yr. Moreover, the spatio-temporal evolution of the ground-motion phenomena is highly nonlinear. These results are in good agreement with previous studies focused on groundwater use in Manila and in the Marikina Fault Valley, suggesting a plausible interpretation of the processes causing surface motion. Incidentally, the ground motions are affecting the locations of several geodetic instruments, including a tide gauge with sea-level records starting in 1902, two permanent GPS (Global Positioning System) stations, and a DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) station. A major implication of those large and locally variable ground motions is that they impede the use of the nearby GPS and DORIS data to correct the tide-gauge records and to derive robust sea-level trends associated with climate change.