Monitoring the Campi Flegrei caldera by exploiting SAR and geodetical data: recent results and future applications
Paolo Berardino(1), Sven Borgstrom(2), Ida Aquino(2), Francesco Casu(1), Carlo Del Gaudio(2), Riccardo Lanari(1), Michele Manunta(1), Mariarosaria Manzo(1), Antonio Pepe(1), Susanna Pepe(1), Giovanni Pasquale Ricciardi(2), Ciro Ricco(2), Eugenio Sansosti(1), Giuseppe Solaro(2), Piero Tizzani(1) and Giovanni Zeni(1)
(1) IREA - CNR, Via Diocleziano, 328, 80124 Napoli, Italy
(2) INGV - OV, Via Diocleziano, 328, 80124 Napoli, Italy
Differential Synthetic Aperture Radar Interferometry (DInSAR) is a remote sensing technique that allows investigating earth surface deformation phenomena (with centimeter to millimeter accuracy) by exploiting the round-trip phase components of Synthetic Aperture Radar (SAR) images relative to an area of interest.
In particular, we refer to the Small BAseline Subsets (SBAS) technique , which relies on the use of small baseline differential SAR interferograms and on the application of the singular value decomposition (SVD) method. This technique can generate deformation velocity maps and time-series of the area of interest; moreover, it has the peculiarity to be able to work at two-scale resolution in order to investigate both spatially large deformation phenomena (with resolutions of about 100m x 100m)  and localized displacements that may affect, for example, small areas or single buildings (at the full instrument resolution) .
The SBAS algorithm large scale feature has been proved to be well suited for characterizing and monitoring of volcanic phenomena. This has the big advantage of reducing the amount of data to be handled, thus making the whole processing chain more efficient with respect to the full resolution one, while keeping the capability to measure the deformation signal related to the volcanic activity.
The geodetical monitoring of the Neapolitan Volcanic District via an integration between DInSAR and classical geodetic techniques is going on in the frame of an agreement between the Italian National Institute of Geophysics and Volcanology (INGV) and the Institute for the Remote Sensing of the Environment of the Italian National Research Council (IREA-CNR).
In this work we will show recent results (extending from 2002 to date) on the Campi Flegrei (Phlegrean Fields) caldera, a volcanic and densely populated area located to the west of the city of Naples (Italy), obtained by using all the ENVISAT ASAR available data from both ascending (track: 129 - frame: 810) and descending (track: 36 - frame: 2781) orbits; moreover, we combined ascending and descending data in order to separate the vertical and horizontal components of the deformation velocity .
The processed data revealed that the recently detected new uplift phase of Campi Flegrei, which became very clear in summer 2005 with an average velocity of about 2.8 mm/year, has definitely reduced the uplift velocity since spring 2007. This conclusion is consistent with independent deformation measurements carried out by the Vesuvius Observatory (INGV-OV).
Differences, in terms of limits and potentialities of InSAR with respect to classical techniques and vice-versa, are a very interesting matter of debate indicating, as an optimal solution for monitoring purposes in active volcanic areas, the integration of all the available techniques.
Finally we note that, within the framework of the Italian Space Agency (ASI) pilot project “Volcanic Risk System”, the most recent SBAS ENVISAT data processed at IREA-CNR are displayed in the monitoring room of the Vesuvius Observatory through an optical fibre connection between the two institutes. Moreover, with the availability of data from the newly launched COSMO-SkyMed sensor, this activity will be also extended to X-band data.
 P. Berardino, G. Fornaro, R. Lanari, E. Sansosti: “A new Algorithm for Surface Deformation Monitoring based on Small Baseline Differential SAR Interferograms”, IEEE Transactions on Geosci. and Remote Sensing, Vol. 40, N. 11, pp. 2375-2383, November 2002.
 R. Lanari, O. Mora, M. Manunta, J. J. Mallorquí, P. Berardino, E. Sansosti: “A Small Baseline Approach for Investigating Deformations on Full Resolution Differential SAR Interferograms”, IEEE Transactions on Geosci. and Remote Sensing, Vol. 42, N. 7, pag. 1377-1386, July 2004.
 P. Lundgren, F. Casu, M. Manzo, A. Pepe, P. Berardino, E. Sansosti, R. Lanari, “Gravity and magma spreading of Mount Etna volcano revealed by radar interferometry”, Geophysical Research Letters, Vol. 31, No. 4, L04602, doi:10.1029/2003GL018736, 17 February 2004..
 IREA web GIS system, http://www.irea.cnr.it/webgis/terra.html.
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,