Estimate and Modeling of Vertical Ground Displacements by Space and Terrestrial Techniques in the Northern Adriatic, Italy

The Northern Adriatic area, in Italy, including coastal regions, is affected by high rates of natural subsidence greatly enhanced, during last century, by anthropogenic components mainly due to ground fluid exploitation. To measure and model vertical crustal movements is of major importance for the presence of natural lowlands and coastal lowlands which are exposed to the risks of flooding events due to river overflow or to the occurrence of extreme storm events. Sea-level rise resulting from increasing global temperature is an additional threat to this region. A network of permanent GPS stations, extending from the southern Po River Plain to the area around Venice, is in place since several years. At most of the stations, in addition to GPS, other geodetic observation techniques such as gravity and InSAR allow for validation of the individual time series, for continuous monitoring in space and time of vertical movements by combining GPS and InSAR, and for a better understanding of the geodynamical processes in the area. Three tide gauge stations with centennial time series, co-located with the GPS systems, are available. The vertical land movements can be removed from the tide gauge records in order to derive absolute sea-level time series. A comparison with satellite altimetry data is performed at the three coastal stations, although this is not an easy task because the satellite data are limited due to the narrow shape of the Adriatic basin. The GPS network data have been re-analyzed by using ITRF2005 and the vertical rates have been estimated. These results are compared to those provided by absolute and relative gravimetry and InSAR data.