Preliminary Results of GPS Studies for Monitoring Land Subsidence Over the Shallow Gas Reservoir in India

Anthropogenic land subsidence is associated with the removal of subsurface material during activities such as underground mining operations, underground construction, and withdrawal of natural resources like water, oil, and gas. In south Gujarat province of India, gas has been extracted from shallow depth for the last two and half years. To measure land subsidence over the study area, a precise GPS monitoring network was established in February 2004 with four reference stations and 27 deformation stations. GPS repeat observations have been carried out over this network to study land subsidence, during February 2004 to May 2006 with geodetic dual-frequency GPS receivers by GPS team, Indian Institute of Technology Bombay. The results of nine campaigns, to estimate the subsidence are discussed in this paper. One of the major causes of land subsidence over this area is gas extraction; hence the observed subsidence is compared with the production of hydrocarbon and pressure depletion. A high correlation is found between land subsidence and hydrocarbon production.