126,711 research outputs found
Attenuation and velocity structure in the area of Pozzuoli-Solfatara (Campi Flegrei, Italy) for the estimate of local site response
No full textIn the present work I infer the 1D shear-wave velocity model in the volcanic area of Pozzuoli-Solfatara using the dispersion properties of both Rayleigh waves generated by artificial explosions and microtremor. The group-velocity dispersion curves are retrieved from application of the Multiple Filter Technique (MFT) to single-station recordings of air-gun sea shots. Seismic signals are filtered in different frequency bands and the dispersion curves are obtained by evaluating the arrival times of the envelope maxima of the filtered signals. Fundamental and higher modes are carefully recognized and separated by using a Phase Matched Filter (PMF). The obtained dispersion curves indicate Rayleigh-wave fundamental-mode group velocities ranging from about 0.8 to 0.6 km/sec over the 1-12 Hz frequency band.
I also propose a new approach based on the autoregressive analysis, to recover group velocity dispersion. I first present a numerical example on a synthetic test signal and then I apply the technique to the data recorded in Solfatara, in order to compare the obtained results with those inferred from the MF analysis
Moreover, I analyse ambient noise data recorded at a dense array, by using Aki’s correlation technique (SAC) and an extended version of this method (ESAC) The obtained phase velocities range from 1.5 km/s to 0.3 km/s over the 1-10 Hz frequency band.
The group velocity dispersion curves are then inverted to infer a shallow shear-wave velocity model down to a depth of about 250 m, for the area of Pozzuoli-Solfatara. The shear-wave velocities thus obtained are compatible with those derived both from cross- and down-hole measurements in neighbour wells and from laboratory experiments. These data are eventually interpreted in the light of the geological setting of the area.
I perform an attenuation study on array recordings of the signals generated by the shots. The attenuation curve was retrieved by analysing the amplitude spectral decay of Rayleigh waves with the distance, in different frequency bands. The attenuation curve was then inverted to infer the shallow Q inverse model.
Using the obtained velocity and attenuation model, I calculate the theoretical ground response to a vertically-incident SH-wave obtaining two main amplification peaks centered at frequencies of 2.1 and 5.4 Hz. The transfer function was compared with that obtained experimentally from the application of Nakamura’s technique to microtremor data, artificial explosions and local earthquakes. Agreement between the two transfer functions is observed only for the amplification peak of frequency 5.4 Hz.
Finally, as a complementary contribution that might be used to the assessment of seismic risk in the investigated area, I evaluate the peak ground acceleration (PGA) for the whole Campi Flegrei caldera and locally for the Pozzuoli-Solfatara area, by performing stochastic simulation of ground motion partially constrained by the previously described results. Two different methods (Random Vibration Theory (RVT) and ground motion generated from a Gaussian distribution (GMG)) are used, providing the PGA values of 0.04 g and 0.097 g for Campi Flegrei and Pozzuoli-Solfatara, respectively
On Venetian Campi Resilience to Climate Change
No full textVenice is known for its history and beauty and its fragility and potential demise. The city is experiencing an increase in yearly average temperatures affecting outdoor - indoor comfort and average energy expenditure. Owing to existing literature demonstrating how local microclimate depends on urban density, shape, and orientation of buildings and materials, the work studies the influence of changing Venice temperatures by targeting such issues, focusing on an urban fabric typical form, known as Campi. Based on IPCC's future weather predictions for 2050 scenario A1B, the work highlights how the urban fabric configuration affects the local microclimate and outdoor conditions to define how buildings will mitigate and adapt to environmental transitions. The method couples microclimate and outdoor comfort users' perception of Physiological Equivalent Temperature (PET), via ENVI-met. Preliminary results show that the compactness of the urban fabric in Venetian Campi significantly reduces outdoor temperatures due to the increased density of shadow areas in the courtyard or in narrow Venice streets. The role of water is also simulated via ENVI-met, as buildings' materials and indoor energy consumption are assumed as invariant to evaluate the historic urban fabric climate resilience. The results constitute a first step towards understanding to what extent a particular urban fabric type is thermally resilient.Environmental Technology and Desig
Geochemical study of the Solchiaro (Procida Island,Campi Flegrei) eruptive products by microthermometry and microanalyses of fluid and melt inclusions.
No full textThis study presents the work I have done during the 4 years of a PhD program that was part of the internationalization programme of the Italian research system approved by the Ministero della Ricerca e dell’Università (MIUR) between the Università degli Studi di Napoli “Federico II”, (Dipartimento di Scinze della Terra) and the Virginia Polytechnic Institute and State University (Department of Geosciences).
107 selected melt inclusion (MI), 77 open glasses, 80 olivines and 7 bulk rocks (from 4 representative samples of Solchiaro eruption) were analyzed for major/trace element and volatiles. Mostly, olivine compositions vary from Fo82 to Fo88 with one maximum value of Fo90. 2 group of MI were recognized based on major element composition: 1) K2O-rich MI with composition that is the same of bulk rock in the literature and 2) K2O-poor MI that instead have been never reported from previous study of the Phlegrean Volcanic District (PVD). The first group consists of 95% of the melt and relates mostly to within plate setting whereas the second group consists of around 5% of the melt and relates to subduction setting. Magma associated with Solchiaro eruption evolved under open system processes as suggested by petrographic evidence and glass compositions. H2O-CO2 concentrations dissolved in glass suggest that magma was saturated in volatiles at least at 12.5 km depth and continuously degassed during the Solchiaro eruption. Maximum depths are in agreement with other studies based on different approaches. Volatile correlations suggest that during closed system degassing, as the Solchiaro eruption progressed, maximum S contents decreased and minimum Cl and F contents increased. The major, trace and volatile evolution of crystals, glass, and MI is consistent with a model that involves either continuous or episodic recharge of the magma chamber ponded at least at 12.5 km depth
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Título: Operum
No full textSign.: *\p4\s, B-4B\p4\sPort. a dos tintasApostillas marginalesError tip. de pag., en la p. 397 consta 401, y de la p. 440 pasa a la 443Sign.: *, B-Z, 2A-2Z, 3A-3Z, 4A-4BPort. a dúas tintasTexto con anotacións marxinaisErro tip. de pax., na p. 397 consta 401, e da p. 440 pasa á 44
Título: Operum ad vniuersam iuris prudentiam philosophiam et litteras humaniores pertinentium
No full textNas port. 2ª e 3ª consta: editio septimaSign.: [ ], [a]-g, a-b, A-Z, 2A-2L, 2M, *, A-Z, 2A-2Q, 2RPort. a dúas tintas e con grav. xilCada parte con port. e pax. propiasTexto con anotacións marxinaisErro de pax., na p. 313 consta 331Vitam auctoris ; Historiam Iuris ciuilis ; Elementa iuris ciuili
b value enlightens different rheological behaviour in Campi Flegrei caldera
No full textThe Campi Flegrei caldera is one of the most dangerous volcanoes in the world and since 2005 it is in unrest. Here we evaluate the 3D tomography of the b value at the Campi Flegrei volcanic area revealing a very good correlation with the structure of the hydrothermal system involved in the bradiseismic phenomenon. More precisely, we observe the smallest b-values where we expect the higher stress/strain concentration, namely in the caprock, and for the deepest seismicity. Conversely, the largest b values are observed where the porosity of the medium allows the passage of the volcanic gases toward the surface. Values of b close to typical tectonic ones are observed where the presence of faulting structures is well documented
b value enlightens different rheological behaviour in Campi Flegrei caldera
No full textAbstract The Campi Flegrei caldera is one of the most dangerous volcanoes in the world and since 2005 it is in unrest. Here we evaluate the 3D tomography of the b value at the Campi Flegrei volcanic area revealing a very good correlation with the structure of the hydrothermal system involved in the bradiseismic phenomenon. More precisely, we observe the smallest b-values where we expect the higher stress/strain concentration, namely in the caprock, and for the deepest seismicity. Conversely, the largest b values are observed where the porosity of the medium allows the passage of the volcanic gases toward the surface. Values of b close to typical tectonic ones are observed where the presence of faulting structures is well documented
- …
