Apport des donnees TerraSAR-X pour le suivi de l'activite du piton de la fournaise

Abstract

We present preliminary results of an interferometric survey, based on TerraSAR-X data, of Piton de la Fournaise volcano (Reunion Island, Indian Ocean) for the period between September 2009 and January 2010. In a first part of this study, we analyse in detail the benefits of X-band in terms of interferometric coherence from a set of 57 TerraSAR-X interferograms. These benefits are compared with those of C-band, obtained from a set of 340 Envisat ASAR interferograms. As a result, we demonstrate that X-band coherence is significantly better in areas without vegetation than that of C-band and that X-band coherence declines quickly in areas covered with vegetation as expected. We also show that TerraSAR-X coherence can be used to map, with good accuracy, lava flows emplaced during the time spanned by the interferogram. In addition, TerraSAR-X interferograms provide new insight on displacements associated with an intrusion which happened on 18-19 October 2009 and with three eruptions which happened on 5-6 November 2009, 14 December 2009 and 2-12 January 2010. A qualitative analysis of fringe patterns, visible on interferograms, indicates that each period of activity is associated with an inflation of the Central Cone. The sources of inflation are located within the external southern flank of the Dolomieu crater and are coeval with short wavelength deflation of the southern margin of the Dolomieu crater. Such deflations are predicted by theoretical models above dykes, but may also be related to sliding of the southern rim of the Dolomieu crater and therefore require attention in the future.