Lanari et al. (2002) present deformation data over the Somma-Vesuvius volcanic complex. The volcano is in a quiescent stage but  ground deformation is characterized by continuous subsidence, revealed by ERS satellite data and levelling surveys, between 1992 and 2000.
Deformation is mainly localized in two zones on  the Vesuvius cone and a narrow annular area that, although not fully continuously, extends around the base of the Somma edifice. The authors propose that the subsidence at both sites involces joint effects of gravitational sliding and extensional tectonic stress occurring at the contact between different lithological units.