Comparing and combining space and terrestrial geodetic techniques to monitor crustal deformation

It is of particular importance to define and establish appropriate observational strategies characterized by the ability to measure, with high accuracy, spatially and time continuous deformations of the land surface. An ensemble of space, airborne and terrestrial techniques can be adopted by taking advantage of the complementary strengths of the different observations. We present a network encompassing northeastern Italy, which extends from the Apennines to the southeastern Po Plain and, along the Adriatic coast, to the Venice area and Trieste. First results mainly concern a study of land subsidence performed by comparing and combining different space and terrestrial techniques, which were co-located in several stations of the network. High-accuracy knowledge of subsidence rates is of particular importance in the Venice area for the re-organization of the lagoon territory and for building an adequate protection from increasing sea level and extreme events. Examples are provided for the stations in the network such as Medicina, Bologna and Marina di Ravenna where the available data series are several years long. At Medicina, the results of CGPS, superconducting and absolute gravimeter and InSAR observations, in combination with several meteoclimatic data series, are compared and combined. At the Bologna station, CGPS, absolute gravity and InSAR data are acquired while at Marina di Ravenna, on the Adriatic coast, CGPS and InSAR observations are available. All InSAR data are processed by means of the PS technique, thus obtaining a dense grid of measures over the study area. The ensemble of adopted space and terrestrial techniques will make it possible to acquire a thorough understanding of seasonal, long-term regional/local geophysical phenomena as well as climate-related impacts affecting the station motions.