GNGTS 2015 - Atti del 34° Convegno Nazionale

96 GNGTS 2015 S essione 1.2 The GPS vertical kinematic pattern in the Italian peninsula: characteristics and anthropogenic – geodynamic implications N. Cenni 1 , P. Baldi 1 , M.E. Belardinelli 1 , S. Gandolfi 2 , F. Loddo 3 , E. Mantovani 4 , M. Viti 4 1 Dipartimento di Fisica ed Astronomia, Università degli Studi di Bologna, Italy 2 Dip. di Ingegneria Civile, Chimica, Ambientale e dei Materiali (DICAM), Università degli Studi di Bologna, Italy 3 Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, Italy 4 Dipartimento Scienze Fisiche, della Terra e dell’Ambiente, Università degli Studi di Siena, Italy Introduction. The reconstruction of the present vertical kinematic pattern in the Italian peninsula is the aim of this work. The area is characterized by a complex tectonic setting driven by the interaction of Eurasian, Anatolian – Aegean, and African plates. Therefore the present kinematic patter observed in the area is principally driven from these geodynamic deformation. The most important sedimentary area are interested by natural subsidence and, in some cases by important anthropogenic phenomena, as for example groundwater pumping from a shallow well-developed multiaquifer system and gas production from onshore and offshore reservoirs, which introduce displacements superimposed to the tectonic ones. The magnitude of these anthropogenic displacements, especially in the vertical component, can be comparable or higher than the tectonic contribute and are characterized to important spatial and time variations. In order to reconstruct the present vertical kinematic pattern and its spatial and time variation we have analyzed the GPS observation acquired at several permanent stations located in the Italian peninsula and surroundings. The relatively high density of this network can provide a detailed spatial description of these movements. The relatively long observation time span (larger than 5-6 years) of several sites included in the network considered can give the possibility to investigate the existence and the magnitude of possible time variation in the vertical kinematic field. In some regions, as for example the Po Plain, the monitoring of the subsidence phenomena is realized by public Institutions as I.G.M.I. (Istituto Geografico Militare Italiano) or A.R.P.A. - E.R. (Agenzia Regionale per la Prevenzione e l´Ambiente dell´Emilia-Romagna) by different techniques: leveling, SAR and vertical extensometer. This, provide the possibility to combine and compare the results obtained analyzing GPS data with ones obtained with other techniques in the selected areas. Data analysis. The present velocity field in the Italian peninsula and surroundings has been estimated using the GPS daily observation acquired with a sampling rate of 30 s from 632 permanent stations (Fig. 1). We have analysed the entire data set from January 1, 2001 to April 10, 2015. The phase and pseudo-code data of each continuous GPS site have been analysed by GAMIT software, version 10.4 and following (Herring et al., 2015a) adopting a distributed procedure (Dong et al., 1998). The whole network has been divided into 43 clusters, following a simple geographic criterion, while maintaining the shortest baseline as possible. The observation of the following common stations: AJAC, BRAS, CAGL, GRAZ, IENG, MATE, NOT1, WTZR e ZIMM (Fig. 1) have been included in each cluster. Loose constraints (100 m) have been assigned to the daily position coordinates of each station belonging to all clusters. The International GPS service for Geodynamics ( IGS) precise orbital solutions from Scripps Orbit and Permanent Array Center have been included in the processing with tight constraints, such as the Earth Orientation Parameter. The Phase Centre Variation (PCV) absolute corrections for both ground and satellite antennas are included. The daily loosely constrained solutions of the 43 clusters obtained after GAMIT processing are combined into a unique solution by the GLOBK software (Herring et al. , 2015b) and aligned into the ITRF2008 reference frame (Altamimi et al. , 2012) by a weighted six parameters transformation (three translations and three rotations), using the ITRF2008 coordinates and velocities of the following 13 high-quality common IGS stations: BUCU, CAGL, GRAZ, IENG, LAMP, MARS, MATE, PENC, SFER, SOFI, TLSE, VILL, WTZR,YEBE and ZIMM (inset in Fig.1). At the end of this procedure, the daily time series of the north, east and vertical geographical position components of each site included in the analysis are estimated. In order to obtain a