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Crustal Deformation of the Alban Hills Volcanic Complex (Central Italy) by Permanent Scatterers Analysis

Cristiano Tolomei(1) and Claudio Prati(2)

(1) INGV, via Vigna Murata, 605, 00143 Roma, Italy
(2) Politecnico di Milano, via Ponzio 34/5, 20133 Milano, Italy


Surface deformation of the Alban Hills volcanic complex, SE of Rome, Italy, has been measured using the Permanent Scatterers technique. This recently developed InSAR technique has allowed to improve the measurement accuracy of surface deformations, providing estimates of ground displacement velocity of mm/years over stable natural targets. The PS technique is based on the analysis of time series of SAR images. Only the natural targets showing a good stability of the backscattered signal in all the amplitude images (PS) are selected to calculate the interferometric phase. The analysis technique allows to estimate and remove the tropospheric contribution from the phase signal and then to reconstruct the ground displacement trend for each PS, in the SAR line of sight. The PS technique has been applied to the Alban Hills area using 66 ERS1- 2 images relative to descending orbits and 33 images from ascending orbits, acquired in the period June 1992- December 2000. Over 100,000 PS were identified; their velocities confirm the presence of considerable ground deformation around the most recent craters, allowing to define the deformation patterns with high spatial resolution. We validated the PS velocities using leveling data. We modeled the ascending and descending velocity fields using the analytical solutions by Okada (1985) for a rectangular, purely tensile dislocation in an elastic half space. We defined two alternative models for the inflation sources: 1) a single N-S sill with vertical tensile component (U3); 2) two smaller sills differently oriented with similar U3 components. Our work shows that the dense spatial sampling of the deformation field allows to constrain more accurate source models than previously available, improving the estimate of source depth, location and geometry.


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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