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InSAR monitoring of Faial and Pico islands (Azores), first results.

Joana Martins(1), Joao Catalao(1), Petar Marinkovic(2) and Ramon Hanssen(2)

(1) University of Lisbon, IDL, LATTEX, Faculdade de Ciencias, 1749-016 Lisboa, Portugal
(2) DEOS, Delft University of Technology, Kluyverweg 1, 2629 HS Delf, Netherlands


Faial and Pico islands (Azores archipelago) have a considerable volcanic-tectonic activity and have been monitored with GPS for the last decade. The point wise structure of GPS observations has only given a small number of point’s kinematics. KARMA project intents to overcome this limitation aimed at the determination of deformation partition over Faial and Pico islands using INSAR. The small dimension of this islands and the fast temporal decorrelation due to abnormal weather conditions and large vegetated areas are the challenging topics of this project. The persistent scatterers technique was tentatively implemented and evaluated on this extreme condition case. Two non consecutive years of ENVISAT-ASAR C-band images were used, from March to October 2004 and from March 2006 to June 2007, in descending and ascending mode. The master image was selected minimizing the perpendicular and temporal baseline and the image of October 2004 was selected. With this image, multiple differential interferograms (12 in the total) were computed using DORIS software. The interferograms show poor coherence due to temporal decorrelation, high vegetated areas and high atmospheric variability compromising the interferogram analysis and interpretation. Even though, some landslides were identified on the flanks of Pico volcano and an estimation of its volume was determined. The PS technique was applied to overcome the reduced coherence problem but the low number of PSC (Persistent Scatterers Candidates) estimated in 12 interferograms resulted in none PS. Some improvements on the algorithm are now being made and it is believed that the installation of 6 artificial trihedral corner reflectors next November will contribute positively to a readable solution. In this presentation the main results of INSAR processing and PS technique feasibility over these islands will be illustrated and analyzed.


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