[J09-5] Geodesy and seismology general contributions V

[J09-5-02] Detection and Measurement of Land Subsidence Using InSAR and GPS in the Sabana de Bogota, Colombia, South America

^○Hector Mora-Paez¹, Takeshi Sagiya², Takeo Ito², Estelle Chaussard³, Shimon Wdowinski⁴ (1.Colombian Geological Survey, Space Geodesy Research Group, Bogota, Colombia, 2.University of Nagoya, Japan, 3.University at Buffalo, USA, 4.Florida International University, USA)

The Sabana de Bogota is located in the Eastern Cordillera of Colombia, and represents a tectonic-sedimentary basin consolidated after the final upheaval of the Northern Andes, around 5 Ma, (van der Hammen et al, 1973; Wigninga, 1996). Inside the Sabana de Bogota is located Bogota, the capital city of the country, with approximately 8 million inhabitants. Since land subsidence is a major human-induced geological hazard that affects buildings and urban infrastructure and results in severe economical consequences for both individuals and local government administrations, it is important to estimate the subsidence in the Sabana de Bogota plain using both InSAR and GPS techniques. Analysis of ALOS data acquired during 2008-2011, TERRASAR-X acquired during 2013-2015 and SENTINEL-1 acquired during 2014-2016 shows a distributed subsidence pattern, both in urban areas and agricultural areas outside Bogota city. The observed subsidence occurs most likely due to groundwater withdrawal from the local aquifer. A reprocessed height time series of GPS stations indicates that the International GNSS Services BOGT station shows a linear height trend of -44.2 ± 0.2 mm/yr (Rudenko et al., 2013). Since there was only one GPS station in the Sabana de Bogota area, (BOGT), the Colombian Geological Survey (through the Space Geodesy Research Group) installed a continuous GPS station at the El Rosal site (VROS) and built some field stations. These new sites will enable increased comparison between InSAR and GPS observations. In addition, under an agreement between the Colombian Geological Survey and the Bogota Land Cadastre Administrative Office, a network of GNSS stations has been deployed. InSAR shows subsidence up to 6-7 cm/yr while GPS stations show subsidence up to 4-5 cm/yr. We plan to continue monitoring the subsidence using GNSS and InSAR techniques and collecting water well data for analysis, in order to provide our finding to both local authorities and the public.