GNGTS 2015 - Atti del 34° Convegno Nazionale

GNGTS 2015 S essione 2.1 31 identify increase in water levels interpretable as the result of the long lasting compression of confined aquifers. The Emilia 2012 seismic sequence is followed in both clusters by a water level fluctuation slightly recognizable also in the preparatory stage of 2010-2012. In particular signal pattern seem to be similar in both clusters. Anyway only a comprehensive analysis with all recorded parameters could reveal eventual precursory patterns and better highlight these water level features. Time series of gas components recorded in northern and central Italy. In the framework of the project INGV-DPC S3, a database was created containing radon data collected and provided by scientific institutions or volunteer, accompanied, when available, by meteorological data recorded by the radon instruments, or from meteorological stations located near the site of detection of radon. The database includes 3,961 sites and more than one million data (Riggio and Santulin, 2015). Since the final objective is a joined interpretation, first among radon data from different sites, and then, among all the observable analyzed within the project, homogenization of data, by daily sampling, has been carried out. For a more accurate evaluation of the data, it was decided to remove by the time series any effects caused by meteorological parameters, such as, in particular, temperature and pressure. For this purpose the Origin software used and the methodology of the PCA (Principal Component Analysis) has been used. For the Cazzaso site, the correction was minimal, showing a lack of dependence of radon from atmospheric influences. In other cases, an influence of the temperature is detected, but didn’t not affect the determination of the anomalous periods. The values of temperature and pressure were acquired by the instrument itself or by meteorological stations, near the site of radon detection. In almost all the series, short and long term anomalies, has been highlighted. Since, in some cases, seasonal variations are more evident in the signal of radon, and could affect the interpretation, this component has been eliminated by averaging the signal day by day, over one year, and repeated for all years. The cross-correlation between the sequence calculated daily and the original signal gave a correlation coefficient greater than 0.8. Trying to find a method that matches all time series, the Autosignal software was used, which, through the Lomb analysis, enables the use of time series even with interruptions during the acquisition. The annual component has been eliminated in the radon signal. The time series detrended from such component have been considered for PCA to verify possible correlations (similar behaviour during time) between the various sites. In present times the OGS group is also carrying out a study about radon degassing activity and RETIRA index jointly with the UR3 based in Potenza. Satellite data could be, in principle, correlated to degassing activity and first results should be available during next times. The first phase of the work has concerned the data processing by RST techniques (e.g. Tramutoli et al. , 2013) of dissolved CO 2 measured in the water points of the IGG - CNR network. The IGG – CNR network, operating since late 2002, is currently constituted by six continuous automatic monitoring stations, installed in the areas of highest seismic risk of the Tuscany region: Garfagnana, Lunigiana, Mugello, Upper Tiber Valley and Mt. Amiata. The data series of the Equi Terme (MS) spring, delivered at DPC-INGV during the 2012-2013 period, were not appropriate for the type of processing required by the project in the 2013-2014 period, as all parameters show a remarkable variability over time due to the influence of local rains on the deep circulation. For this reason it was considered more appropriate to complement the study with the data processing of dissolved CO 2 recorded at the Gallicano station, whose parameters have shown less variability over time compared to the Equi Terme spring. With an average flow rate of about 1.5 L/s, the Gallicano thermo-mineral spring emerges at an altitude of m 209 a.s.l. in the Serchio Valley, Garfagnana region, discharging high salinity waters (2.4 to 4.2 g/L) with a temperature of 23.4°C to 25.2°C. (Pierotti et al. , 2015 and reference therein). The Gallicano spring was monitored for geochemical seismic precursors because of: i) its geographical proximity to the main geological structures suspected to be the seismogenic sources of the strongest earthquakes recorded in the Garfagnana region; ii) the deep origin of the thermal waters discharged by the