ALBERT

Description: Studying seismicity in a volcanic environment provides important information on the state of activity of volcanoes. The seismicity of the Neapolitan volcanoes, Campi Flegrei, Vesuvius, and Ischia, shows distinctive characteristics for each volcano, coveringwide range of patterns and types. In this study we relocated some significant volcano- tectonic earthquake swarms that occurred in Campi Flegrei and Vesuvius. Moreover, we compared the earthquake occurrence evolution, the magnitude and the seismic energy release of the three volcanoes. Also, we considered the results of seismic analysis in the light of geochemical and ground deformation data that contribute to defining the state of activity of volcanoes. In Campi Flegrei, which is experiencing a long term unrest, we identified a seismogenic structure at shallow depth in Pisciarelli zone that has been activated repeatedly. The increasing seismicity accompanies an escalation of the hydrothermal activity and a ground uplift phase. At Vesuvius a very shallow seismicity is recorded, which in recent years has shown an increase in terms of the number of events per year. Earthquakes are usually located right beneath the crater axis. They are concentrated in a volume affected by the hydrothermal system. Finally, Ischia generally shows a low level of seismicity, however, in Casamicciola area events with a moderate magnitude can occur and these are potentially capable of causing severe damage to the town and population, due to their small hypocentral depth (typically 〈 2.5 km). After the seismic crisis of August 21, 2017 (mainshock magnitude M 4), the seismicity returned to a low level in terms of occurrence rate and magnitude of earthquakes. The seismicity of these three different volcanic areas shows some common aspects that highlight a relevant role of hydrothermal processes in the seismogenesis of volcanic areas. However, while the main swarms in Campi Flegrei and most of the Vesuvian earthquakes are distributed along conduit-like structures, the seismicity of Ischia is mainly located along faults. Furthermore, the temporal evolution of seismicity in Neapolitan volcanic area suggests a concomitant increase in the occurrence of earthquakes both in Campi Flegrei and Vesuvius in recent years.

Description: Published

Description: 662113

Description: 4V. Processi pre-eruttivi

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.