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Measurements of ground subsidence in Mokpo using PSInSAR and SBAS

Sang-Wan Kim(1,2), Shimon Wdowinski(2), Timothy H. Dixon(2), Falk Amelung(2), Joong-Sun Won(3) and Jeong Woo Kim(1)

(1) Sejong University, 98 Gunja-dong Gwangjin-gu, Seoul 143-747, Korea
(2) University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
(3) Yonsei University, 134 Shinchon-dong Seodaemun-gu, Seoul 120-749, Korea


Many urban areas are experiencing land subsidence due to various causes, including a withdrawal of groundwater, oil and natural gas, underground excavation, mining and tectonic motion. The impacts of land subsidence are specifically serious on coastal cities. Where the elevation of land is close to or below sea level, it is highly susceptible to flooding, for example, New Orleans by Hurricane Katrina. Aquifer system compaction associated with ground water withdrawal or drainage of organic soil often shows continuous, but waning slow movement with time due to residual compaction even after ground water level reaches stable. In reclaimed land, more rapid and waning subsidence of the ground surface usually results from increased loads that accelerate soil compaction to stabilize the land. Here we demonstrate interferometric mapping of surface deformation related to soil consolidation. Twenty three JERS-1 SAR images acquired from 1992 to 1998 were used to estimate land subsidence rate in the city of Mokpo, located in the south western coast of Korea. Large regions within Mokpo are subjected to significant subsidence because about 70% of the city is a reclaimed land. By applying both permanent scatterer InSAR (PSInSAR) adopting hyperbolic models and Small Baseline Subset (SBAS), two subsidence field maps were retrieved in order to measure and predict the waning ground subsidence. The both results indicated continuous subsidence in several areas with different decaying velocity. The subsidence velocity reached over 6 cm/yr in the most rapidly sinking area. The estimated subsidence rates were verified by comparison with ENVISAT C-band SAR measurements acquired during 2004-2005. Hyperbolic model applied to the JERS PSInSAR results allowed us to predict more precisely the subsidence occurred during ENVISAT acquisitions. The result confirms that PSInSAR technique with hyperbolic model is valuable for long-term monitoring of land subsidence characterized by time-varying velocity.


Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry