Subsidence of Campi Flegrei (Italy) detected by SAR interferometry

Seven ERS SAR images of the Napoli area acquired from 1993 to 1996 were use d to create six differential interferograms. Although the ambiguity height of the selected couples is high, because of the adverse characteristics of the area, the interferograms exhibit a relatively low level of coherence, e ven for couples sampling short time intervals. According to the estimated a ccuracy, no deformation is observed on Vesuvio volcano. The best interferog ram, corresponding to the period Feb. 14, 1993 - Apr. 3, 1996, shows that t he centre of the Campi Flegrei caldera, near Pozzuoli harbour, subsided by about three fringes (84 mm) during the three years interval. This result is consistent with the value of 28 +/- 2 mm/year obtained from routine levell ing surveys over the same period in the same area. The deflation that start ed after the 1983-1984 seismic and inflation crisis is thus still significa nt. The modelling of the fringe pattern, assuming a spherical deflating sou rce within an elastic half-space medium, predicts a source centred about 80 0 m Southwest of Pozzuoli at a depth of 2.7 +/- 0.3 km. For the studied tim e window, the maximum subsidence predicted by the model is 25 mm/year.