Germani, Carlo

Seven years after the signing of an agreement, called IPODATA, between the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the Società Speleologica Italiana (SSI), we report some results related to data recorded in artificial cavities and caves. IPODATA was born with the aim of selecting cavities which match specific criteria to host Very Broad Band seismometers. These instruments have high sensitivity over the entire frequency range of interest in seismology and so are able to record both fast and very slow movement of the soil but require certain site conditions such as thermal ad pressure stability. In the first phase of the activity the speleologists collected the available information about artificial and natural underground cavities. Those sites were then submitted to a screening done by seismologists at desk, on the basis of certain requirements which are explained in detail. Subsequently, through in site inspections, the INGV staff has selected the appropriate sites, both from the point of view of seismology and from that of logistic of installation. In these sites have been carried out tests with portable seismic instrumentation, before the final installation of the stations. We present the results for the sites where temporary or permantent stations of the National Seismic Network were installed. Cavities data are compared to data recorded at other standard stations in the field. In general, underground sites provide better data as they attenuate the natural and anthropogenic disturbances (called "seismic noise"), allowing a more reliable record of ground motion, in practice they permit to record the real seismic waves during earthquakes. This fact is certainly of interest and may be an incentive to resolve the little but inevitable problems that we encounter in cavities installations, particularly in the transmission of real-time data from the underground stations to the data center at INGV. - - - - - - - - - - - - - - - - - - - - - - - - RIASSUNTO A sette anni dalla stipula della convenzione IPODATA tra Istituto Nazionale di Geofisica e Vulcanologia (INGV) e Società Speleologica Italiana (SSI), riportiamo alcuni risultati relativi ai dati registrati in ipogei. Scopo di IPODATA è individuare cavità ipogee idonee ad ospitare sismometri a “Larga Banda” cioè ad alta sensibilità su tutta la gamma di frequenze di interesse sismologico. Tali strumenti sono infatti capaci di registrare sia movimenti veloci sia lentissimi del suolo ma richiedono particolari caratteristiche del sito, ad esempio la stabilità termica. L’attività è consistita in un prima fase di ricognizione, da parte degli speleologi, di siti ipogei artificiali o naturali. È seguita una prima scrematura fatta a tavolino, sulla base di alcuni requisiti indicati dai sismologi ed illustrati nel dettaglio. Successivamente, tramite sopralluoghi, il personale INGV ha selezionato i siti adatti, sia dal punto di vista sismologico sia da quello della logistica d’installazione. In tali siti sono stati effettuati test con strumentazione sismica portatile, prima della installazione definitiva delle stazioni. Vengono presentati i risultati relativi ai siti selezionati dove sono state installate, in modo temporaneo o permanente, stazioni della Rete Sismica Nazionale. I dati ipogei sono confrontati con dati registrati in altre stazioni in superficie. In generale i siti ipogei forniscono dati migliori in quanto attenuano i disturbi di origine naturale ed antropica (detti “rumore sismico”) consentendo una registrazione più fedele del movimento del suolo o meglio delle onde sismiche generate durante i terremoti. Questa peculiarità è sicuramente di stimolo per risolvere i piccoli ma inevitabili problemi che si incontrano nelle installazioni ipogee ed in particolare nella trasmissione dei dati in tempo reale da queste stazioni al centro di acquisizione dati presso la Sala di Monitoraggio sismico dell’INGV

Many lakes have been the object of hydraulic works in historical times, and the drainage tunnel carved by Romans for regulating the level of Lake Albano (Central Italy) can be considered as one of the most important historical hydraulic tunnels in the world. We sampled and analysed lake water, as well as groundwater samples from the Lake Albano emissary and another hydraulic work in the area (Ninfeo), which were analysed for their geochemical and isotopic composition in order to extract useful information for a possible reuse of the tunnel for anthropogenic purposes. The collected water samples exhibit common chemical features, typical of water–rock interaction processes in volcanic areas. Analyses of minor and trace elements confirmed the abovementioned results, indicating the presence of an atmospheric pollution source for heavy metals, although their concentrations are mostly below the Maximum Admitted Concentrations for drinking water issued by the World Health Organization. The chemical composition of dissolved gases indicated that both lake and groundwater are mainly enriched in CO2. Isotopic analyses suggested a clear volcanic origin for CO2 dissolved in lake water, while carbon dioxide in groundwater from the Roman emissary is produced by soil respiration. As further confirmed by Oxygen and Deuterium isotopic composition, the Roman emissary drains local suspended aquifers neither in contact with the lake water body nor influenced by volcanic activity, suggesting the opportunity to use the tunnel as a ‘‘zero-condition’’ monitoring site for individuating a possible future renewal of volcanic activity.

Groundwater from karst circulation systems of Central Italy were sampled and analyzed, in 2018, for delineating a preliminary, general geochemical framework of their relationship with neotectonics, in an area characterized by a frequent and often destructive seismicity. We determined field physical-chemical parameters, concentrations of main dissolved ions and gases and isotopic composition of water ( 18O, D) and total dissolved inorganic carbon ( 13C TDIC). We discriminated between “normal” hydro-karst systems and multi-component aquifers, composed of meteoric groundwater that have also interacted with rocks of di erent lithological nature and/or deep fluids. These multicomponent aquifers are of potential interest in the monitoring of neotectonics activity, because changes in the stress field associated with the preparatory phase of an earthquake may a ect the permeability of rocks, in turn causing variation of their chemical-isotopic character. The geographical distribution of these aquifers seems to be controlled by tectonics. In fact, the Olevano–Antrodoco–Sibillini thrust separates the more anomalous sites, located westwards of it, from the groundwater bodies at its eastern side, showing a more typical karst character.