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Detection and characterisation of the topographic surface displacements using DINSAR and PS interferometry applied to the Nord/Pas-de-Calais coal basin.

Yann Gueguen(1), Benoit DEFFONTAINES(2), Marwan AL HEIB(3), Bénédicte FRUNEAU(2), Daniel RAUCOULES(4), Marcello DE MICHELE(4), Yves GUISE(4) and Jean PLANCHENAULT(4)

(1) UMLV - INERIS, IFI - 5 Bd Descartes - Champs-sur-Marne, 77454 Marne-la-Vallée cedex 2, France
(2) UMLV, IFI - 5 Bd Descartes - Champs-sur-Marne, 77454 Marne-la-Vallée cedex 2, France
(3) INERIS, Ecoles des Mines de Nancy - Parc de Saurupt, 54042 Nancy Cedex, France
(4) BRGM, 3 av. Claude Guillemin - BP 36009, 45060 Orléans Cedex 2, France


Various phenomena can induce displacements of the topographic surface and thus cause disorders in structures and infrastructures. Their origins are numerous, in particular in the Nord/Pas-de-Calais coal basin where the extraction of underground resources was considerable. The exploitation of mine in this area is completed since 1992 but the residual subsidence can cover a long period of about 4 to 6 years after the end of the exploitation. Nevertheless, the major part of subsidence occurs during active mine and the amplitude of this residual subsidence is usually very small compared to the total subsidence and thus could be confused with other natural and/or anthropic phenomena. Charbonnages de France is in charge of the monitoring of the area of Nord/Pas-de-Calais (France) and continues to use high precision levelling comparison for surveying the surface. This traditional method presents many disadvantages and the interferometry techniques could offer a serious help to quantify the residual subsidence and identify the other phenomena which may induce deformations of the same order of amplitude. In this study, both differential SAR Interferometry (DINSAR) and Persistent Scaterrers Interferometry (PSI) are used to estimate deformation during a 15 years period (1992 to 2007) after the end of exploitation. 88 ERS scenes, distributed on two adjacent tracks, and 19 ENVISAT scenes are processed, using DIAPASON software for DINSAR and GAMMA-IPTA for PSI. The area undergoes high temporal decorrelation due to the high amount of vegetation. Nevertheless, deformations are well detected; they present low amplitude with a maximum rate of only 1 cm/y during 5 to 7 years after the end of the exploitation. The results obtained by interferometry are initially compared with the traditional methods of levelling and show a good agreement. The development of a methodology allowing the comparison and the identification of the various sources of depressions is then possible, in particular for the phenomenon of residual mining subsidence. It shows the difficulties to discriminate the different processes which could involve deformations in this area.


Workshop presentation

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