A comparison of SBAS and PS ERS InSAR for subsidence monitoring in Oslo, Norway

Tom Rune Lauknes(1) , John Dehls(2) , Yngvar Larsen(1) , Kjell Arild Høgda(1) , and Dan J. Weydahl(3)

(1) Norut IT, Po. Box. 6434, NO-9294 Tromsø, Norway
(2) Geological Survey of Norway, Geological Survey of Norway, NO-7431 Trondheim, Norway
(3) Norwegian Defence Research Establishment, Po. Box. 25, NO-2027 Kjeller, Norway


There have been four earthquakes in the Oslo region in Norway between 1994 and 1999. Their strength has been from 2.5 to 3.6 on Richter's scale. In addition, there has been a lot of tunnel construction work in Oslo over the last 10 years. This has caused subsidence of several mm at different places around the city. The InSAR technique has been shown to be a valuable tool for subsidence monitoring in many different places of the Earth. Interpretation of the multi-temporal interferometric SAR signal is a real challenge due to complex topography, dominating large areas with coniferous forest outside the built-up areas, and seasonal variations with snow and freezing several months per year.

In this paper, we present the results achieved using the Small-Baseline Subset (SBAS) differential InSAR technique for land deformation monitoring and compares the results with results obtained by the Permanent Scatter (PS) technique and land surveillance measurements. We will also discuss differences between the two methods.

The PS InSAR processing was performed by Tele-Rilevavento Europa for the Geological Survey of Norway on two independent series of radar images. This was possible due to the large overlap between images from neighboring orbits at this high latitude. 42 images from track 108 and 48 images from track 337 were processed, covering the time period 1992-2002.

The SBAS ERS InSAR dataset was processed from raw data to SLC by Norwegian Defence Research Establishment, applying the EETF algorithm. A total of 43 ERS SAR raw data sets from descending satellite track 337 and frame 2394 were received from ESA, covering the time period 1992-2000. The SBAS algorithm was implemented on top of the Norut IT in-house InSAR processing system.

Both techniques show significant subsidence in several areas. Different selection of stable points will give slightly different velocity values when comparing the two results. However, the subsidence pattern is nearly identical for the two methods.


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