Multi-temporal mapping of land subsidence at basin scale exploiting Persistent Scatterer Interferometry: case study of Gioia Tauro plain (Italy)

The temporal and spatial evolution of the pumping-induced ground subsidence in the Gioia Tauro plain (Southern Italy) is investigated exploiting multi-temporal analysis of PSInSAR (Permanent Scatterer Interferometric Synthetic Aperture Radar) data from ERS 1/2 (1992-2001) and ENVISAT (2002-2006) satellites. The PSInSAR derived ground deformation velocity maps and related displacement time series reveal that subsidence rates as high as 10-15 mm/yr are observed in 1992-2006, with the highest velocities (up to 23 mm/yr) occurring between 1992 and 2000 in the central portion of the Plain. Ascending and descending data are combined to extract the vertical and east-west components of ground motions, and reveal the presence of predominant components in the vertical direction due to the compaction of Quaternary sediment in the basin. Aquifer compaction is a consequence of groundwater abstraction. An acceleration index is computed to synthesize the temporal changes between the observed displacements in the two intervals, 1992-2001 and 2002-2006. Deceleration of motions is observed in most of the plain with velocity reductions of about 65% from 1992-2001 to 2002-2006; only a few narrow areas in the southern sector reveal significant increases of motion velocities in the 2002-2006 period, with subsidence velocities exceeding by about 30% those observed in 1992-2001.