Land Subsidence Monitoring over Gas Reserve Using Global Positioning System

Abstract

Anthropogenic land subsidence are associated with the removal of subsurface material during activities such as under¬ground mining and construction, and withdrawal of natural resources like water, oil, and gas. Most of the major subsidence areas around the world due to human activity have developed in the past half-century at accelerated rates due to rapidly increasing use of ground water, oil and gas etc. The heterogeneous subsidence in urban areas damage buildings and man-made structures. Subsidence due to such activities is pervasive throughout the world, and is recognized as a problem of international importance, because of financial loss in repairing infrastructure damages. Hence, accurate measurement and monitoring techniques are required, to measure and monitor subsidence and to protect infrastructure lying over the surface. Most common land subsidence monitoring technique is geodetic levelling. The accuracy of geodetic leveling is very high, but it is time consuming, tedious, labour intensive and expensive operation. Hence, with the development of new space technologies, land subsidence is now increasingly being measured with the Global Positioning System (GPS). GPS is a satellite based navigation and surveying system for determination of precise position and time using radio signals from the satellites. GPS is widely used for numerous applications, including land subsidence. IIT, Bombay team has carried out GPS survey over the gas/oil reservoir to monitor land subsidence near Surat region. Results of this study and other factors responsible for land subsidence are discussed in this paper.