Surface deformation analysis in the Ischia Island (Italy) based on spaceborne radar interferometry |
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| Institution: | 1. Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Via Diocleziano 328, Napoli, Italy;2. Università degli Studi di Salerno, Dipartimento di Fisica “E.R. Caianiello”, Via Giovanni Paolo II 132, Fisciano, Salerno, Italy;3. Università degli Studi di Napoli Federico II, Dipartimento di Scienze Fisiche, Via Cintia, Napoli, Italy;4. Dipartimento di Scienze della Terra, Università di Perugia, Piazza dell''Università, 06123 Perugia, Italy;1. Institute of Environmental Assessment and Water Research (IDAEA), CSIC, c/Jordi Girona 18, 08034 Barcelona, Spain;2. Department of Geotechnical Engineering and Geosciences, Universitat Politècnica de Catalunya (UPC), Jordi Girona 1-3, 08034 Barcelona, Spain;3. Associated Unit: Hydrogeology Group (UPC-CSIC), Spain;4. University of Liege, ArGEnCo, GEO3, Hydrogeology and Environmental Geology, Aquapôle, B52/3 Sart-Tilman, 4000 Liege, Belgium;5. Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Division of Geomatics, Av. Gauss 11, E-08860 Castelldefels, Barcelona, Spain;1. Norut, P.O. Box 6434, N-9294 Tromsø, Norway;2. Department of Geosciences, UiT-The Arctic University of Norway, P.O. Box 6050 Langnes, N-9037 Tromsø, Norway;3. Geological Survey of Norway, P.O. Box 6315 Sluppen, N-7491 Trondheim, Norway;4. Norwegian Mapping Authority, P.O. Box 600 Sentrum, N-3507 Hønefoss, Norway |
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| Abstract: | The island of Ischia, located at the northwestern end of the Gulf of Napoli (Italy), is a volcanic area that is historically active (the Arso eruption, in 1302 and the Casamicciola earthquake, in 1883) and has diffuse hydrothermal phenomena. We present in this work a study of the surface deformation occurring in the island, which is based on applying the Differential Synthetic Aperture Radar Interferometry (DInSAR) algorithm referred to as Small BAseline Subset (SBAS) technique. This study is focused on the 1992–2003 time interval and SAR data acquired by the European Remote Sensing (ERS) satellites from ascending and descending orbits have been used, thus allowing us to discriminate the vertical and east–west components of the displacements. A validation of the DInSAR results has been carried out first by comparing the vertical deformations estimated from the SAR data with those measured from the spirit leveling network that is present in the area. In particular, we computed the difference between the mean vertical deformation velocities estimated from the SAR and the corresponding geodetic measurements along three main leveling lines; the maximum value of the root mean square difference is of about 1 mm/yr. The final discussion is dedicated to the interpretation of the detected displacements, benefiting from the overall information extracted from the ascending and descending DInSAR measurements. In particular, DInSAR data relative to the vertical deformation component show that the present-day subsidence of Ischia mainly develops in areas characterized by active landsliding and along faults; moreover, the deflation of the island, which is recorded by the horizontal displacement component, is probably related to the de-pressurization of the hydrothermal system. |
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