Seismic analysis of the Asinelli Tower and earthquakes in Bologna

The existence of a valuable historical heritage of the Medieval age in Bologna has motivated a deeper study on the seismic behaviour of the Asinelli Tower, which, beyond being the town symbol, has a structural configuration prone to seismic damage. Accordingly, in the present paper, the seismicity of Bologna is reviewed and a synthesis of the damage observed in the urban area, based on an accurate historical research, is given, with the objective of evaluating the behavior of the Asinelli Tower within the framework of the effects localized in the municipality. An assessment of the tower's stability with respect to compatible seismic events, at least qualitatively, with the region seismicity is then carried out by means of a non-linear dynamic analysis on a simplified model.     

A statistical analysis of flank eruptions on Etna volcano

A singularly complete record exists for the eruptive activity of Etna volcano. The time series of occurrence of flank eruptions in the period 1600–1980, in which the record is presumably complete, is found to follow a stationary Poisson process. A revision of the available data shows that eruption durations are rather well correlated with the estimates of the volume of lava flows. This implies that the magnitude of an eruption can be defined directly by its duration. Extreme value statistics are then applied to the time series, using duration as a dependent variable. The probability of occurrence of a very long (300 days) eruption is greater than 50% only in time intervals of the order of 50 years. The correlation found between duration and total output also allows estimation of the probability of occurrence of a major event which exceeds a given duration and total flow of lava. The composite probabilities do not differ considerably from the pure ones. Paralleling a well established application to seismic events, extreme value theory can be profitably used in volcanic risk estimates, provided that appropriate account is also taken of all other variables.     

Il decisivo contributo italiano allo sfruttamento delle acque termali

Riassunto L'A., dopo aver riassunto i principali tentativi fatti all'estero per lo sfruttamento industriale delle acque termali, descrive le proprie esperienze per il miglioramento degli impianti a vapor d'acqua, nonchè di quelli a fluido intermedio per i quali ultimi, con la collaborazione del Prof. D'Amelio è stato recentemente realizzato all'Isola d'Ischia il primo impianto italiano di tal tipo, funzionante con buon rendimento, sfruttando quelle acque termali.

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Zusammenfassung Nach Erwähnung der wichtigsten Versuchen zur industriellen Ausnützung der warmen Wasser welche in der Naturlauftreten, beschreibt der Verf. seine eigenen Versuche die zur Verbesserung der Wasserdampfsanlagen geführt haben; ferner diejenigen mit mittelbarer Flüssigkeit, bei welchen es, durch die Mitarbeit von Herrn Prof. D'Amelio, gelungen ist auf der Insel Ischia die erste Anlage zu verwirklichen, welche eine befriedigende Leistung bei Ausnützung der dortigen Thermen zeigt.

     

Reversed responses within a segmented detached breakwater, the Tuscany coast Italy—a case study

A multiple detached breakwater system was designed to protect an extended length of shoreline in front of the presidential villa located in the Gombo region, Tuscany, Italy. The purpose of this empirical field study was to examine the impact of the surface-piercing segmented breakwater on the subaqueous morphology and to follow the effect of the breakwaters on the beach.Shoreline mapping was performed on rectified, stereo-plotted air photos and was also based on topographic field surveying. Bathymetric mapping was based on interpolation of profile lines extending to 10 m water depth.Building the breakwaters in a downstream order caused the trapping of the longshore-driven sediments mainly at the southernmost breakwaters that faced the longshore sediment supply. The longshore down-current direction controlled the hierarchy of the beach response. Two relatively coherent behavioral domains were found to exist: (1) the “permanent tombolo stage” of segments 1–3 and (2) the “no sinuosity” response of the beach opposite the northern segment no. 5. The segment no.4, in-between, did not exhibit a coherent behaviour, indicating a drastic reversal in the sedimentary regime.The three southernmost tombolos facing the longshore current became the main sediment trap, causing a lee-side erosional effect to emerge within the protection scheme of the segmented detached breakwaters. The oblique incident waves enter through the gaps and maintain in the inshore the depleted longshore drift, causing the shoreline configuration in the lee of the northern breakwaters to develop into a prograding log-spiral bay.     

THE MARBLE BEACHES OF TUSCANY*

ABSTRACT. Beach‐nourishment operations designed to replace sediment lost through erosion change the identity and meaning of coastal landscapes. Seven beaches in Tuscany, nourished with marble‐quarry waste, reveal how an industrial byproduct is naturalized by particle rounding and sorting and can become a positive symbol of human‐altered nature. The marble was placed on formerly sandy beaches, resulting in different grain size and color of sediments, beach morphology, and value for human use. The abrasion rate of marble makes the nourished beaches unsatisfactory when viewed solely as protection structures, but the rapid particle rounding and aesthetic appeal of marble increase the acceptability of the beaches for recreation.     

The European Upper Mantle as Seen by Surface Waves

We derive a global, three-dimensional tomographic model of horizontally and vertically polarized shear velocities in the upper mantle. The model is based on a recently updated global database of Love- and Rayleigh-wave fundamental-mode phase-anomaly observations, with a good global coverage and a particularly dense coverage over Europe and the Mediterranean basin (broadband stations from the Swiss and German seismic networks). The model parameterization is accordingly finer within this region than over the rest of the globe. The large-scale, global structure of our model is very well correlated with that of earlier shear-velocity tomography models, based both on body- and surface-wave observations. At the regional scale, within the region of interest, correlation is complicated by the different resolution limits associated to different databases (surface waves, compressional waves, shear waves), and, accordingly, to different models; while a certain agreement appears to exist for what concerns the grand tectonic features in the area, heterogeneities of smaller scale are less robustly determined. Our new model is only one step towards the identification of a consensus model of European/Mediterranean upper-mantle structure: on the basis of the findings discussed here, we expect that important improvements will soon result from the combination, in new tomographic inversions, of fundamental-mode phase-anomaly data like ours with observations of surface-wave overtones, of body-wave travel times, of ambient “noise”, and by accounting for an a-priori model of crustal structure more highly resolved than the one employed here.     

Modelling the cosmological co-evolution of supermassive black holes and galaxies – I. BH scaling relations and the AGN luminosity function

We model the cosmological co-evolution of galaxies and their central supermassive black holes (BHs) within a semi-analytical framework developed on the outputs of the Millennium Simulation. This model, described in detail by Croton et al. and De Lucia and Blaizot, introduces a 'radio mode' feedback from active galactic nuclei (AGN) at the centre of X-ray emitting atmospheres in galaxy groups and clusters. Thanks to this mechanism, the model can simultaneously explain: (i) the low observed mass dropout rate in cooling flows; (ii) the exponential cut-off in the bright end of the galaxy luminosity function and (iii) the bulge-dominated morphologies and old stellar ages of the most massive galaxies in clusters. This paper is the first of a series in which we investigate how well this model can also reproduce the physical properties of BHs and AGN. Here we analyse the scaling relations, the fundamental plane and the mass function of BHs, and compare them with the most recent observational data. Moreover, we extend the semi-analytic model to follow the evolution of the BH mass accretion and its conversion into radiation, and compare the derived AGN bolometric luminosity function with the observed one. While we find for the most part a very good agreement between predicted and observed BH properties, the semi-analytic model underestimates the number density of luminous AGN at high redshifts, independently of the adopted Eddington factor and accretion efficiency. However, an agreement with the observations is possible within the framework of our model, provided it is assumed that the cold gas fraction accreted by BHs at high redshifts is larger than at low redshifts.