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SAR interferometry monitoring of landslides on the Stromboli volcano

Paolo Farina(1) and Letizia Guerri(1)

(1) University of Firenze, V. la Pira 4, 50121 Firenze, Italy


A major landslide occurred on the steep NW flank (Sciara del Fuoco) of Stromboli on December 30th 2002, following an intensification of the explosive activity of the volcano and the descent of a lava flow within the Sciara del Fuoco itself. The landslide, which has an estimated volume of more than 30 million cubic meter, partially extended below the sea level and caused a tsunami which produced severe loss along the island shores. After this event, the National Civil Protection Department decided to install an innovative system for monitoring surficial ground deformations on the flank of the Sciara del Fuoco. This apparatus, which was extensively tested by our research group for landslide monitoring, consists of a ground-based SAR (Synthetic Aperture Radar) interferometer, known as LISA (Linear SAR). The specific version of the instrument installed in Stromboli has been called InGRID-LISA, acronym of Interferometric Ground-based Imaging Deformeter, and it is capable of producing a radar image of the observed area every 12 minutes, with a pixel resolution of about 1 m x 1.5 m, operating at frequencies of 17GHz. The interferometric analysis of sequences of consecutive images allowed us to derive the entire deformation field of the observed portion of the Sciara del Fuoco and of the crater with a millimetric accuracy. InGRID-LISA is a completely remote-sensing technique, implemented via ground-based sensors installed in a stable zone in front of the area to be monitored. This fact, and the possibility of obtaining multi- temporal images showing deformation fields, represent elements of absolute innovation in the realm of deformation monitoring. The technique has been successfully tested in a series of applications on active landslides in Europe but it is applied for the first time in a volcanic environment. InGRID-LISA is continuously active since February 20th 2003 and produces about 120 images per day of the area under investigation. During this period it was possible to follow in detail the deceleration phase of the landslide of December 30th and it was also possible to detect and monitor the displacement pattern over a wide area just below the NE crater, due probably to the incipient detachment of a rockslide of about 1.5 million cubic metres. The collected data can be employed in the framework of a global monitoring network for early-warning purposes, since they provide information over a wide area (about 2 km2), with a high accuracy and observation frequency. The preliminary results from the Stromboli volcano show how the new technique is suitable for an operational use aimed at monitoring ground deformation on active volcanoes.


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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