Characteristics of the low energy seismicity of central Apulia (southern Italy) and hazard implications

The central part of the Apulia region, in southern Italy, has been generally considered practically free from significant level of seismicity, but historical documentation, geological indicators and recent instrumental observations suggest that the activity of local minor tectonic structures could have been masked (and partly also induced) by that of major seismogenic structures located in the neighbouring regions. A revision of the central Apulia seismicity characteristics was conducted considering its space and time distribution, energy release rate and focal mechanisms, in view of possible hazard implications. To better constrain the seismicity rates inferable from the set of available historical data, special attention was paid to the declustering of a catalogue of low energy events (magnitude < 3.5) instrumentally detected in about 20 years: a new declustering procedure, useful for cases like to the one at hand, was purposely devised taking into account the peculiarity of local seismicity characteristics and the limitations of the available database. The results obtained by combining instrumental and historical data show that this area is affected by a rather sporadic seismicity, likely associated to a general tensional regime and possibly stimulated by the interaction with Apenninic and northern Apulia seismogenic activity. Even though less energetic, the local seismicity contributes to increase the moderately damaging shaking probability due to the activity of seismic sources located in the near areas, so to justify the adoption of at least a minimum level of caution in relation to the local definition of seismic protection measures.     

Temporal variability of ultraviolet cloud features in the Venus stratosphere

Statistics on the temporal variability of uv cloud features on Venus during 66 days of nominal mission imaging by the Pioneer Venus Orbiter Cloud Photopolarimeter reveal at least five types of systematic variability on large scales: (1) a low-latitude global-scale wave of period 3.94 ± 0.1 days corresponding to longitudinal motion of the dark equatorial band and propagating westward relative to the mean flow; (2) a midlatitude wave of period 5.20 ± 0.2 days corresponding to wavenumber 1 oscillations of the latitude of the bright polar bands and propagating eastward relative to the mean flow; (3) ～2- to 3-week fluctuations in the slope of longitudinal cloud brightness power spectra at intermediate wavenumbers manifested by variations in the intensity of large bow-shaped features; (4) ～2-month variations in polar region brightness consistent with polar brightening episodes observed from Earth; and (5) a monotonic decrease in the disk-integrated brightness of Venus during the nominal mission which may be either a true time variation or a solar-locked longitudinal dependence of brightness. Small-scale features appear to correlate with large-scale albedo patterns. Specifically, cellular features exist primarily where large-scale dark material is present, while the orientation of streak features with respect to latitude circles oscillates with the same ～4-day period as the large-scale features at low latitudes. The wide range of time scales present in the data suggests the complexity of Venus stratospheric dynamics. Extended observations over many years may be becessary to define the general circulation.     

The earliest temperature observations in the world: the Medici Network (1654–1670)

This paper presents the earliest temperature observations, scheduled every 3–4 h in the 1654–1670 period, which have been recovered and analysed for the first time. The observations belong to the Medici Network, the first international network of meteorological observations, based on eleven stations, the two main ones being Florence and Vallombrosa, Italy. All observations were made with identical thermometers and operational methodology, including outdoor exposure in the shade and in the sunshine to evaluate solar heating, state of the sky, wind direction and precipitation frequency. This paper will consider only the regular temperature series taken in the shade. The observations were made with the newly invented spirit-in-glass thermometer, also known as Little Florentine Thermometer (LFT). The readings have been transformed into modern units of temperature (°C) and time (TMEC). The LFT has been analysed in detail: how it was made, its linearity, calibration and performances. Since the middle of the LIA, the climate in Florence has shown less than 0.18°C warming. However, although the yearly average showed little change, the seasonal departures are greater, i.e. warmer summers, colder winters and unstable mid seasons. The temperature in the Vallombrosa mountain station, 1,000 m a.m.s.l, apparently rose more, i.e. 1.41°C. A discussion is made on the interpretation of this finding: how much it is affected by climate change or bias. A continuous swinging of the temperature was observed in the Mediterranean area, as documented by the long instrumental observations over the 1654–2009 period. However, changes in vegetation, or exposure bias might have contributed to reduce the homogeneity of the series over the centuries.     

A new insight on the decreasing sea level trend over the Ionian basin in the last decades

Altimetry measurements over the Ionian region and tide gauge records along the southern Italian coasts have been combined to analyse the negative sea level trend over the Ionian basin in the last decades. The apparent decreasing trend should be better understood as an abrupt sea level drop in 1998 probably linked to changes in the surface circulation in the Ionian basin induced by the Eastern Mediterranean Transient, which changed from anticyclonic to cyclonic about March 1998. From then onwards, a rising rate of 7.9 ± 0.9 mm/year is observed over the basin.     

Pressure dependence of viscosity of rhyolitic melts

Viscosity of silicate melts is a critical property for understanding volcanic and igneous processes in the Earth. We investigate the pressure effect on the viscosity of rhyolitic melts using two methods: indirect viscosity inference from hydrous species reaction in melts using a piston cylinder at pressures up to 2.8 GPa and direct viscosity measurement by parallel-plate creep viscometer in an internally-heated pressure vessel at pressures up to 0.4 GPa. Comparison of viscosities of a rhyolitic melt with 0.8 wt% water at 0.4 GPa shows that both methods give consistent results. In the indirect method, viscosities of hydrous rhyolitic melts were inferred based on the kinetics of hydrous species reaction in the melt upon cooling (i.e., the equivalence of rheologically defined glass transition temperature and chemically defined apparent equilibrium temperature). The cooling experiments were carried out in a piston-cylinder apparatus using hydrous rhyolitic samples with 0.8-4 wt% water. Cooling rates of the kinetic experiments varied from 0.1 K/s to 100 K/s; hence the range of viscosity inferred from this method covers 3 orders of magnitude. The data from this method show that viscosity increases with increasing pressure from 1 GPa to 3 GPa for hydrous rhyolitic melts with water content ?0.8 wt% in the high viscosity range. We also measured viscosity of rhyolitic melt with 0.13 wt% water using the parallel-plate viscometer at pressures 0.2 and 0.4 GPa in an internally-heated pressure vessel. The data show that viscosity of rhyolitic melt with 0.13 wt% water decreases with increasing pressure. Combining our new data with literature data, we develop a viscosity model of rhyolitic melts as a function of temperature, pressure and water content.     

Deformation during exhumation of medium‐ and high‐grade metamorphic rocks in the Variscan chain in northern Sardinia (Italy)

The Anglona and SW Gallura regions represent key places to investigate the tectonic evolution of medium‐ and high‐grade metamorphic rocks cropping out in northern Sardinia (Italy). From south to north we distinguish two different metamorphic complexes recording similar deformation histories but different metamorphic evolution: the Medium Grade Metamorphic Complex (MGMC) and the High Grade Metamorphic Complex (HGMC). After the initial collisional stage (D1 deformation phase), both complexes were affected by three contractional deformational phases (D2, D3 and D4) followed by later extensional tectonics. The D2 deformation phase was the most significant event producing an important deformation partitioning that produced localized shearing and folding domains at the boundary between the two metamorphic complexes. We highlight the presence of two previously undocumented systems of shear belts with different kinematics but analogous orientation in the axial zone of Sardinia. They became active at the boundary between the MGMC and HGMC from the beginning of D2. They formed a transpressive regime responsible for the exhumation of the medium‐ and high‐grade metamorphic rocks, and overall represent a change from orthogonal to orogen‐parallel tectonic transport. Copyright © 2008 John Wiley & Sons, Ltd.     

Angular Momentum Distribution in Galaxies and Inner Haloes Profile

We study the problem of the determination of a high precision cosmological mass function, which is of fundamental importance in several problems of astrophysics, like the building up of an halo model. The determination of a mass function through numerical simulation is time demanding, and restrict to particular cosmological parameters. Analytical methods, allow to determine high precision mass functions, without the limitations of the simulations. We improve on previous analytical models, reaching high level of precision. In particular, we improve the scheme of Del Popolo presented in older and more recent papers, based on the excursion set approach. We further improve the mass function with respect to the quoted papers, using an higher order first crossing distribution, and an improved barrier with respect previous papers. As a result, we can obtain a mass function with a precision of 1%, in the mass range ≃ (10⁹−10¹⁵) h⁻¹M☉, and in the redshift range 0 < z s< 10. The paper also shows how the use of the quoted improved first-crossing distribution, improves the agreement between the conditional mass function, and simulations.

     

MARC: a robust method for multiple-aspect trajectory classification via space,time, and semantic embeddings

ABSTRACT

The increasing popularity of Location-Based Social Networks (LBSNs) and the semantic enrichment of mobility data in several contexts in the last years has led to the generation of large volumes of trajectory data. In contrast to GPS-based trajectories, LBSN and context-aware trajectories are more complex data, having several semantic textual dimensions besides space and time, which may reveal interesting mobility patterns. For instance, people may visit different places or perform different activities depending on the weather conditions. These new semantically rich data, known as multiple-aspect trajectories, pose new challenges in trajectory classification, which is the problem that we address in this paper. Existing methods for trajectory classification cannot deal with the complexity of heterogeneous data dimensions or the sequential aspect that characterizes movement. In this paper we propose MARC, an approach based on attribute embedding and Recurrent Neural Networks (RNNs) for classifying multiple-aspect trajectories, that tackles all trajectory properties: space, time, semantics, and sequence. We highlight that MARC exhibits good performance especially when trajectories are described by several textual/categorical attributes. Experiments performed over four publicly available datasets considering the Trajectory-User Linking (TUL) problem show that MARC outperformed all competitors, with respect to accuracy, precision, recall, and F1-score.     

Did the “Autochthonous” European foreland of Corsica Island (France) experience Alpine subduction?

Despite the important role played by the Sardinia‐Corsica block in the reconstruction of the Western Mediterranean geodynamics, the extent of involvement of the “Autochthonous” European margin exposed in Corsica (France) (i.e., Hercynian Corsica) in the Alpine orogeny remains uncertain. Stratigraphic and sedimentological studies in the post‐Variscan deposits on the Hercynian Corsica are scarce and even scarcer are the structural and metamorphic constraints. To face these uncertainties, we present new stratigraphic, structural and metamorphic data from the area of Razzo Bianco, Central Corsica, where a complete sequence belonging to the European continental margin is exposed. Field and structural investigations demonstrate that the sequence represents the easternmost edge of the downgoing European plate. Metamorphic studies on the Eocene deposits indicate that the margin was buried at depth up to blueschist facies conditions and, subsequently, it was progressively exhumed mainly through the activation of oblique top‐to‐the NW shear zones.