Evaluation of the use of PSInSAR for the monitoring of subsidence in Oslo region

Timely identification of subsidence is important in order to ensure that remediation efforts are successful. Even if subsidence cannot be prevented or stopped, it must be accounted for in new construction planning. Identification and monitoring of ground deformation can be accomplished using, a number of surveying techniques. Levelling and GPS are both expensive and the number of benchmarks that can be controlled is limited. Since the early 1990's satellite-based radar interferometry has been used to identify large ground movements due to earthquakes and volcanic activity.Data stacking methods that take advantage of a growing archive of radar images, as well as increasing computing power, have led to a large increase in the precision of the technique. Both linear trends and seasonal fluctuations can be identified using the Permanent Scatterers technique. The Geological Survey of Norway has been experimenting with the use of radar interferometry to detect fault movements and landslides, as well as subsidence. Recently, we have tested the feasibility of using the technique to monitor subsidence due to underground construction. The well-known subsidence caused by groundwater drainage during the construction of the Romeriksporten tunnel presents a perfect test case. In addition, subsidence in Oslo centre was examined to better understand the processes involved and possibly establish as basis for future monitoring. Subsidence due to the tunnelling activity was identified successfully in numerous buildings. Displacement-time series obtained by radar interferometry are in close agreement with those obtained by traditional surveying techniques. The onset of subsidence from west to east is in close agreement with the rate of tunnel construction. The city of Oslo's network of benchmarks was first levelled in 1927. This network can be used to measure large-scale subsidence phenome

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