1,721,074 research outputs found
Modelling of CO2 circulation in the Colli Albani area
No full textThe Colli Albani is a quiescent volcano located near the city of Roma, characterized by
the presence of an active geothermal system, periodic seismic swarms and intense diffuse degas-
sing. Several accidents, some lethal, have occurred in recent years associated with episodes of more
intense releases and outbursts of volcanic gases, predominantly CO2 and H2S. Gas emissions pre-
sently comprise the most hazardous phenomenon for the highly populated Colli Albani area, and
there is always the potential for the occurrence of seismic activity. This chapter presents numerical
modelling of heat and fluid circulation, applied to study the mechanisms that control the diffuse
degassing at Colli Albani volcano. Multi-phase and multi-component simulations were carried
out using the TOUGH2 geothermal simulator in a realistic geological context, which includes
all available information on the stratigraphy and structure of the Colli Albani substrate, together
with data on the total gas flux, the local geothermal gradient, the local hydrogeology and the
thermal characteristics of the rocks. The geothermal reservoir at Colli Albani is hosted by the
2000 – 3000-m-thick Mesozoic – Cenozoic carbonatic succession, capped by Pliocene clays that
act as an aquiclude and are few hundreds to over 1000 m thick, which are in turn covered by con-
tinental sedimentary and volcanic deposits that host the shallow hydrogeological system. Numeri-
cal simulations evaluate the effects associated with the thickness of the carbonatic basement and its
cap rock, the role of CO2 supply rate at depth, and the influence of permeable channel-ways through
the cap rocks. Numerical simulations show that the thickness of the geothermal reservoir hosted by
the carbonatic basement and of its impervious cover control the vigour of the convection, the extent
and depth (and hence temperature) of the lateral recharge area, and the distribution of the CO2
within the system. This result suggests that the temperature distribution and diffuse degassing at
the surface reflect not only the characteristics of the heat and fluid source at depth, but also the
specific structure and hydrological properties of the site where they are measured
Volcanic eruption induced floods. A rainfall-runoff model applied to the Vesuvian Region (Italy).
No full textExplosive events are commonly accompanied or followed by heavy rains. These eruption- induced storms together with the deposition of large amounts of ash contribute to destabilise the hydrological cycle in the areas affected by volcanic eruptions. Flooding of the region surround- ing the active volcano can easily follow, increasing the complexity of the volcanic crisis and its management. This is particularly true in the case of Vesuvius, that is not only characterized by a dramatic volcanic hazard, but it is also located within an area that is normally prone to flood hazard. A complete assessment of the impact associated with explosive volcanic eruptions should involve a flood hazard assessment for the region. This work represents a first attempt to address the problem: a topographically based rainfall-runoff model was here applied to the Vesuvian area where two main sub-basins were analysed. The model was applied to evaluate the role of selected parameters on the total discharge at the basins’ outlet. These parameters were chosen among those likely to be affected by an explosive event and were varied through a reasonable range. Results confirm that the deposition of large amounts of ash can affect the temporal evolution of the discharge and its maximum value, for a given precipitation event. The simulations presented outline the need for a detailed flood forecasting study for the Vesuvian area, that should be included within the hazard mitigation strategies.Published223–2455V. Dinamica dei processi eruttivi e post-eruttiviJCR Journa
Signals from the Campi Flegrei hydrothermal system: Role of a “magmatic” source of fluids
No full textThis is a parametric study that was carried out to investigate the signals generated by a
hydrothermal system fed by a pulsating source of magmatic fluids. This study focuses on
the effects that selected properties of the source have on the evolution of hydrothermal
activity at Campi Flegrei, Italy. Numerical simulations are carried out to describe a
multiphase and multicomponent hydrothermal system. Each simulation describes a short
unrest phase, followed by a prolonged quiet period. During the unrest, specific properties
of the fluid source (flow rate, fluid composition, source size, and unrest duration) are
modified with respect to selected baseline values. The evolution of the system is tracked
by looking at two parameters that can be monitored in active volcanic areas: the
composition of fumarolic gases and gravity changes. The results describe the temporal
evolution of these two observables and allow comparisons of the effects of different source
properties. All of the simulated unrest events cause measurable changes in gas
composition and gravity. For the geometry and system properties considered, these
changes always last beyond the end of the unrest period, and can often persist for
decades. Fluid flow rate is the source property that mostly affects the observable
evolution. Gravity is more sensitive to source properties than gas composition, and it
undergoes the largest and quickest changes. The results also highlight the major role that
rock properties and initial conditions have in the evolution of these observable signals.Department of Civil ProtectionPublishedB052013.6. Fisica del vulcanismo4.3. TTC - Scenari di pericolosità vulcanicaJCR Journalreserve
Hydrothermal fluid circulation and its effect on caldera unrest
No full textThis paper focuses on the role that hydrothermal systems may play in caldera unrest. Changes in the fluid chemistry, temperature, and discharge rate of hydrothermal systems are commonly detected at the surface during volcanic unrest, as hydrothermal fluids adjust to changing subsurface conditions. Geochemical monitoring is carried out to observe the evolving system conditions. Circulating fluids can also generate signals that affect geophysical parameters monitored at the surface. Effective hazard evaluation requires a proper understanding of unrest phenomena and correct interpretation of their causes. Physical modeling of fluid circulation allows quantification of the evolution of a hydrothermal system, and hence evaluation of the potential role of hydrothermal fluids during caldera unrest. Modeling results can be compared with monitoring data, and then contribute to the interpretation of the recent caldera evolution. This paper: 1) describes the main features of hydrothermal systems; 2) briefly reviews numerical modeling of heat and fluid flow through porous media; 3) highlight the effects of hydrothermal fluids on unrest processes; and 4) describes some model applications to the Phlegrean Fields caldera. Simultaneous modeling of different independent parameters has proved to be a powerful tool for understanding caldera unrest. The results highlight the importance of comprehensive conceptual models that incorporate all the available geochemical and geophysical information, and they also stress the need for high-quality, multi-parameter monitoring and modeling of volcanic activity.Accepted3.6. Fisica del vulcanismo4.3. TTC - Scenari di pericolosità vulcanicaope
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
On reconciling the interactions between APETALA2, miR172 and AGAMOUS with the ABC model of flower development
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
On reconciling the interactions between APETALA2, miR172 and AGAMOUS with the ABC model of flower development.
No full textAppropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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