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Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Via Moruzzi, 1, 56124 Pisa, Italy
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- PublicationOpen AccessEarthquake-Related Signals in Central Italy Detected by Hydrogeochemical and Satellite Techniques(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; Central Apennines are one of the highest seismic risk regions in Italy. A number of energetic events (MW > 5) struck the region during the period 2004–2017, killing several hundreds of people (e.g., 294 casualties associated with the August 24th, 2016, MW 6.0 event of Amatrice). These earthquakes impacted piezometric levels, springs discharges, and groundwater chemistry across a large area, even at distances of dozens of kilometers from the epicenters. Here we present a multidisciplinary dataset based on hydrogeochemical and satellite observations associated with the seismic events that occurred in Central Italy during the period 2004–2017, which combines information derived from the application of groundwater monitoring and satellite techniques. Groundwater monitoring techniques allowed for the detection of hydrogeochemical anomalies in spring and well waters (14 water sampling points in total, with 22 variations larger than 2σ), while satellite techniques were applied to detect time-space variations in ground thermal emissions. We detected two significant, almost synchronous, anomalies in 2009 and 2016–2017 with both techniques, and we tentatively correlated them to crustal deformation processes. Part of the observed signals were detected before mainshocks, and they appear to be related to aseismic slip or to seismic slip eventually induced by minor fluctuations in seismicity. We argue that the combination of two factors, i.e., the shallow depth of local earthquakes and the concurrent deepening of groundwater circulation paths to several km depth, allow for the recording of variations in the stress field by geofluids released at the surface.93 45 - PublicationOpen AccessCorrelation between small earthquakes and CO2 anomalies in spring waters: a statistical experiment on the probability of seismic occurrenceWe correlated carbon dioxide (CO2) time series detected at the Gallicano site in Tuscany, Italy, with low-magnitude earthquakes occurred in the surrounding area between 2017 and 2021. The CO2 irregular component distribution was analyzed by a Pearson type VII fit, and its cumulate probability by the Gauss’s hypergeometric function, to statistically evidence anomalous fluctuations. We calculated the Matthews correlation between gas concentrations and low-magnitude earthquakes by defining a binary occurrence of CO2 anomalies and seismic events. A positive correlation was highlighted by a time lag between the digital series, which resulted in CO2 anomaly detections ahead of the earthquake time of two days. The correlated earthquakes were mainshocks of local magnitude 1.2 to 3.6, with epicenters within 40 km from the Gallicano site. Correlations among rainfalls, CO2 concentrations and earthquakes were also considered, showing that only few rainfall events were followed by a CO2 anomaly, mostly a day late.
35 13 - PublicationRestrictedEarly signals of new volcanic unrest at Campi Flegrei caldera? Insights from geochemical data and physical simulations(2012)
; ; ; ; ; ;Chiodini, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Caliro, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;De Martino, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Avino, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Gherardi, F.; Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Via Moruzzi, 1, 56124 Pisa, Italy; ; ; ; For the fi rst time a physical model, constrained by monitoring data, is used to derive a quantitative estimate of the evolution in time of magmatic gases that enter a hydrothermal system of an active volcano. The site is Campi Flegrei (west of Naples, in Italy), a caldera that had a large ground infl ation in 1982–1984 followed by 20 yr of subsidence. More recently the behavior of the system has changed: the magmatic component of fumaroles has increased, swarms of earthquakes are more frequent, and the ground has started a general uplifting trend, indicating that the hydrothermal system undergoes repeated injections of magmatic fl uid. Physical simulations of the process show that total injected fl uid masses are the same order of magnitude as those emitted during small to medium size volcanic eruptions, and their cumulative curve highlights a current period of increasing activity. Gas emission studies coupled with physical modeling can be extremely effective in predicting magmatic evolution and eruptive activity at volcanoes.548 50 - PublicationOpen AccessTectonic-Related Geochemical and Hydrological Anomalies in Italy during the Last Fifty Years(2021)
; ; ; ; ; ; ; ; ; ; ; ; ; Seismic hazard reduction policies usually utilize earthquake catalogues and probability evaluations of occurrence. Further geophysical and geochemical parameters could contribute to hazard reduction policies as is currently the case in some countries, such as Iceland, Taiwan, China and Russian Federation. In the past four decades, intense research activity carried out by many different institutions in Italy has allowed us to recognize the most relevant sensitive sites for detecting acceleration in crustal deformation processes by means of geofluids monitoring. All scientific papers published in the period 1976–2020 concerning tectonic-related signals in geofluids have been considered. An in-depth review of previous and present-day research activities, as well as an update of two unpublished time series recorded in Central and Southern Italy, has contributed to identifying areas where an instrumental array is still lacking and the most relevant priority areas for monitoring activities in geofluids. An atlas of all experimental sites utilized in recent decades has been obtained with the purpose of contributing to identifying the most suitable monitoring areas.55 61 - PublicationOpen AccessGeofluids as a possible unconventional tool for seismic hazard assessment(2023)
; ; ; ; ; ; ; In recent decades, phenomenological methods known as Recognition of Earthquake-Prone Areas (REPA) were set up for identifying potential sites of powerful earthquakes. The information on potential earthquake sources provided by the REPA method is an essential part of seismic hazard assessment methodology. For the first time, we have combined global-scale information on the geographic occurrence of geofluids with global-scale information on earthquake occurrence, heat flow distribution, and S-wave dispersion, to gain insights into the evolution of local stress-strain fields. We focused on areas characterized by the occurrence of thermal waters and/or by the release of deep-seated gases, as traced by the isotope composition of associated helium. We noticed that the geographic distribution of these geofluids could serve as an indirect indicator of crustal permeability anomalies generated by crustal deformation procedures. This study proposes adding geofluids to the list of fundamental geological parameters to be considered in hazard assessment research.34 5 - PublicationOpen AccessCross-Correlation among Seismic Events, Rainfalls, and Carbon Dioxide Anomalies in Spring Water: Insights from Geochemical Monitoring in Northern Tuscany, ItalyVariations in the CO2 dissolved in water springs have long been observed near the epicenters of moderate and strong earthquakes. In a recent work focused on data collected during the 2017–2021 period from a monitoring site in the Northern Apennines, Italy, we noticed a significant correlation between CO2 anomalies and moderate-to-weak seismic activity. Here, we extended this analysis by focusing on data collected from the same site during a different period (2010–2013) and by integrating the CENSUS method with an artificial neural network (ANN) in the already-tested protocol. As in our previous work, a fit of the computed residual CO2 distributions allowed us to evidence statistically relevant CO2 anomalies. Thus, we extended a test of the linear dependence of these anomalies to seismic events over a longer period by means of binary correlations. This new analysis also included strong seismic events. Depending on the method applied, we observed different time lags. Specifically, using the CENSUS methodology, we detected a CO2 anomaly one day ahead of the earthquake and another anomaly eleven days ahead. However, no anomaly was observed with the ANN methodology. We also investigated possible correlations between CO2 concentrations and rain events and between rain events and earthquakes, highlighting the occurrence of a CO2 anomaly one day after a rain event of at least 10 mm and no linear dependence of seismic and rain events. Similar to our previous work, we achieved a probability gain of around 4, which is the probably of earthquake increases after CO2 anomaly observations.
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