Characterization of GPS time series at the Neapolitan volcanic area by statistical analysis

The GPS time series recorded at the Neapolitan volcanic area reveals a very peculiar behavior. When a clear deformation is observed, the amplitude distribution evolves from a super‐Gaussian to a broader distribution. This behavior can be characterized by evaluating the kurtosis. Spurious periodic components were evidenced by independent component analysis and then removed by filtering the original signal. The time series for all stations was modeled with a fifth‐order polynomial fit, which represents the deformation history at that place. Indeed, when this polynomial is subtracted from the time series, the distributions again become super‐Gaussian. A simulation of the deformation time evolution was performed by superposing a Laplacian noise and a synthetic deformation history. The kurtosis of the obtained signals decreases as the superposition increases, enlightening the insurgence of the deformation. The presented approach represents a contribution aimed at adding further information to the studies about the deformation at the Neapolitan volcanic area by revealing geologically relevant data

Spatial and temporal distribution of vertical ground movements at Mt. Vesuvius in the period 1973-2009

Since the early ’70s vertical ground movements at Mount Vesuvius area have been investigated and monitored by the Osservatorio Vesuviano (Istituto Nazionale di Geofisica Vulcanologia - Osservatorio Vesuviano since 2001). This monitoring began with the installation of a high-precision leveling line in the region at medium-high elevations on the volcano. The deformation pattern and expected strain field assessment methods in the volcanic structure induced by inner sources has demanded in subsequent years the expansion of the leveling network up to cover the whole volcanic area, enclosing part of leveling lines of other institutions. As a result of this expansion, the Mt. Vesuvius Area Leveling Network (VALN) has today reached a length of about 270 km and consists of 359 benchmarks. It is configured in 21 circuits and is connected, westward, to the Campi Flegrei leveling network and, northward, to the Campania Plain leveling network. The data collected have been carefully re-analyzed for random and systematic errors and for error propagation along the leveling lines to identify the areas affected by significant ground movements. For each survey, the data were rigorously adjusted and vertical ground movements were evaluated by differentiating the heights calculated by the various measurements conducted by the Osservatorio Vesuviano from 1973 to 2009

ANALISI DELLE COMPONENTI INDIPENDETI (ICA) NELLO STUDIO DELLE DEFORMAZIONI DEL SUOLO IN AREE VULCANICHE

Independent component analysis (ICA) is a recent and well-known technique used to separate mixtures of signals. This technique has been applied to the ground deformation time-series recorded at the permanent GPS network of the Osservatorio Vesuviano-INGV in order to characterize the deformation background level in the Neapolitan volcanic area. The analysis revealed the presence of five independent periodic signals common at all the GPS stations; some of them are interpreted as effects of earth tides. The residual signal at each station represent the local ground deformation. Unfortunately the ICA cannot provide the absolute amplitude of the components, indeed we are not able to obtain a residual amplitude at each station. Then we used a stationarity analysis in order to investigate the eventual presence of local transient deformations. The ICA technique combined with the stationarity analysis has shown to be a very interesting tool for individuating ground deformation trends and could be very useful in volcanic areas monitoring