Ground deformation in Neapolitan Volcanic Area by NeVoCGPS nerwork

Abstract

The Neapolitan volcanic area,located around the ciry of Naples in the Southern patt of the Campanran plain, is one of the most relevant active volcanic areas, chanctenzed by a hrgh risk, due to the dense urbantzatton and to presence of three active volcanoes (Campi Flegrei caldera, Somma-Vesuvio and Ischià Ishnd). Campi Flegrei caldera, placed west of Naples, is a well known example of peculiar ground deforàations (bradyseism), chanctenzed by period of intense uplift, nor necessarily culminating in an eruptive phase (the last eruption occurred in 1538), followed by a subsidence phase. Recently, during the 1970-1972 and 1,982-1984,t he caldera has been affected by two intense episode of intense uplift (sine eruption). In 1985 a subsidence phase started (with some episodic small and fast uplifts superimposed) and terminated at end of 2004. Somma-Vesuvio, at east of Naples, is a quiescent volcano (the last eruption occurred in 1944) and is charactenzed by a low level of ground deformatio.r, .*..p. small and limited subsidence are s, located near craLter area and around the volcanic edifice. Ischia island, at S\ù7 of Naples, has been characterrzed rn the past times by a both explosive and effusive volcanic activity (the last eruption occurred in 1302). Successively the ground deformation activity has been charactenzed by a meaningful subsidence in the S and NW sectors of the island. Ground deformation is usualy ónnected with pressure changes of magma reservoirs or with intrusive events. So, monitoring and analysis of ground deformations are important tools in order to understanding the geometry, dynamics and evolution of thr source. The NeVoCGPS QNeapolitan Volcanic Continuous GPS) network consists of 25 stations (Fig. 1), managed by remote control. The data are automatically downloaded and proceised daily by the Ultra rapid IGS products. \ù7hen the IGS final orbits and Earth rotation parameters (trRPt become avallable the data are reprocessed and weekly solutionr àr. obtained, also. The data processing is performed by the Bernese Processing Engine (BPE) of the Bernese GPS software v. 5.0 in double difference mode. The èlevaiion cut-off is set at 1'5o and the IGS absolute phase centre variations (APCVO for the satellite and receiver antennas are applied. To minimize the tectonic movements contribution, the GPS position time series are estimated relative to the stable station ENAV located outside the volcanTc area. The NeVoCGPS datahave been always very useful for ground deformadon study, pointing out also small intensity phenome na, that usually are not discriminated by discontinuous measures.