ALBERT

Description: Detection analyses are necessary to plan microseismic networks for use in the monitoring of anthropic activities. In 2014, the Italian Ministry of Economic Development (MiSE) issued guidelines for the monitoring of microseismic activity, ground deformations, and reservoir pore pressure. In 2016, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) was commissioned to carry out specific investigations, aimed at assessing the guidelines applicability at the pilot site of the gas storage concession "Minerbio Stoccaggio" (Bologna). In this work, we present an overview of detection analysis, performed by the INGV team, during the experimental phase of the above mentioned guidelines. Measurements of ambient seismic noise, performed from 1 January 2018 to 31 March 2019, were used to assess detection thresholds of different configurations of the Minerbio Integrated Seismic Network (MISN). Detection analysis is particularly relevant for the Inner Domain of Detection (IDD), the crustal volume centred on the reservoir, within which it is vital to ensure the highest network performance. The results obtained in this work, validated through data recorded by the MISN during the analysed period, show that in the worst noise conditions observable in the area, the final configuration of the MISN enables localising ML ≥ 1.0 events occurring in the whole IDD, in line with the monitoring requirements prescribed by the guidelines.

Description: Published

Description: 203-230

Description: 4T. Sismicità dell'Italia

Description: JCR Journal

Description: The Arctic water cycle is changing dramatically as evidenced by marked shifts in Arctic sea ice conditions, atmospheric processes, and hydrological regimes. Evaporation from the increasingly ice-free Arctic ocean causes moistening of the atmosphere and serves as an unprecedented water source for the Northern Hemisphere. Stable water isotopes (δ18O, δ2H, d-excess) can be used to trace exchange processes between ocean and atmosphere including their potential to feedback into the global climate system. The MOSAiC expedition provided a unique opportunity to collect, analyze, and synthesize discrete samples of the different hydrological compartments in the central Arctic, comprising sea ice, seawater, snow, and melt ponds. Moreover, we present observations of atmospheric humidity, δ18O, δ2H, and d-excess, obtained from a cavity-ring-down spectrometer installed on RV Polarstern and operated continuously during the MOSAiC expedition. By analyzing discrete samples, we found that average seawater δ18O of -1.7±1.95‰ (n=126) conforms to observed and modelled isotopic traits of the Arctic Ocean. Second year ice is relatively depleted compared to first year ice with average δ18O values of -3.1±2.81‰ (n=397) and -0.7±2.28‰ (n=409), respectively. Snow on top of the sea ice (n=303) has the most depleted isotopic signature among all compartments shaping the Arctic water cycle (mean δ18O=-15.3±7.12‰) The atmospheric water vapour dataset reveals a clear seasonal cycle; significant positive correlations are found both with local specific humidity and air temperature. The comparison of synoptic events, characterized by abrupt isotopic fluctuations, with simultaneous observations from land-based Arctic stations indicates a strong influence of sea ice coverage on the isotopic signal. For an in-depth understanding of the isotopic changes, the observations are compared to an isotope-enhanced ECHAM6 atmosphere simulation. The model-data comparison assesses the capability of this state-of-the-art AGCM to capture the first-order evaporation/condensation processes and their seasonal evolution. Our dataset provides a comprehensive description of the present-day isotopic composition of the Arctic water covering a complete seasonal cycle. This will ultimately contribute to resolve the linkages between sea ice, ocean, and atmosphere during critical transitions from frozen ocean to open water conditions.