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Separation of different deformation regimes using InSAR data

Gini Ketelaar(1) and Ramon Hanssen(1)

(1) Delft University of Technology, Faculty CiTG, Thijsseweg 11, 2629 JA Delft, Netherlands

Abstract

Interferometric Synthetic Aperture Radar (InSAR) can be used for analyzing deformation patterns in time and space. The InSAR data consists of interferometric phases of a number of so called Permanent Scatterers [Ferretti et al, 2001] which have consistent and high coherence values throughout time. These PS represent different physical objects in the terrain. Reflections may come from the roof of a building or may be interactions between structures and the surroundings. As PS can be physically different, they may describe deformation patterns caused by different phenomena like gas extraction, ground water level variations or foundation instabilities. Before relating the InSAR deformation observations to different physical causes, groups of PS with different deformation behaviour have to be separated. This leads to the following main questions:

1) In which way is it possible to separate different deformation regimes and how detailed should this separation be? 2) Is it possible to estimate a temporal-spatial model for a deformation regime which accounts for the full deformation signal, e.g. which 'removes' all systematic effects from the histograms of the teststatistics? 3) Is there a correlation between deformation regime, type of Permanent Scatterers, location and possible geophysical processes?

These questions are answered using an InSAR test case. For this test case, interferometric phases and coordinates of an amount of PS are available throughout a certain time span. All PS are classified using cartographic data in a GIS. An a priori variance-covariancematrix for the InSAR deformation data is gained by creating variograms from the data. Different deformation groups of PS are separated using the 'integrated' difference along time between the deformation patterns of all combinations of PS. If it has been possible to separate a deformation regime, an inspection of the type of PS within this regime and their locations is done. A spatial-temporal model is estimated for the deformation regime, for example a polynom or a subsidence bowl. The histograms of the teststatistics are examined on systematic effects. Depending on the outcome of this process, a preliminary prediction may be made about the underlying (geophysical) processes.

 

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Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry