Automatic inspection and analysis of digital waveform images by means of convolutional neural networks

Journal of Seismology - Analyzing seismic data to get information about earthquakes has always been a major task for seismologists and, more in general, for geophysicists. Recently, thanks to the...     

On the crystal structure and compressional behavior of talc: a mineral of interest in petrology and material science

The crystal structure of a natural triclinic talc (1Tc polytype) [with composition: (Mg_2.93Fe_0.06)_Σ2.99(Al_0.02Si_3.97)_Σ3.99O₁₀(OH)_2.10] has been investigated by single-crystal X-ray diffraction at 223 and 170 K and by single-crystal neutron diffraction at 20 K. Both the anisotropic X-ray refinements (i.e. at 223 and 170 K) show that the two independent tetrahedra are only slightly distorted. For the two independent Mg-octahedra, the bond distances between cation-hydroxyl groups are significantly shorter than the others. The ditrigonal rotation angle of the six-membered ring of tetrahedra is modest (α ~ 4°). The neutron structure refinement shows that the hydrogen-bonding scheme in talc consists of one donor site and three acceptors (i.e. trifurcated configuration), all the bonds having O···O ≤ 3.38 Å, H···O ~ 2.8 Å, and O–H···O ~ 111–116°. The three acceptors belong to the six-membered ring of tetrahedra juxtaposed to the octahedral sheet. The vibrational regime of the proton site appears being only slightly anisotropic. The elastic behavior of talc was investigated by means of in situ synchrotron single-crystal diffraction up to 16 GPa (at room temperature) using a diamond anvil cell. No evidence of phase transition has been observed within the pressure range investigated. P–V data fit, with an isothermal third-order Birch-Murnaghan equation of state, results as follows: V ₀ = 454.7(10) Å³, K _T0 = 56(3) GPa, and K′ = 5.4(7). The “Eulerian finite strain” versus “normalized stress” plot yields: Fe(0) = 56(2) GPa and K′ = 5.3(5). The compressional behavior of talc is strongly anisotropic, as reflected by the axial compressibilities (i.e. β(a):β(b):β(c) = 1.03:1:3.15) as well as by the magnitude and orientation of the unit-strain ellipsoid (with ε ₁:ε ₂:ε ₃ = 1:1.37:3.21). A comparison between the elastic parameters of talc obtained in this study with those previously reported is carried out.     

Fluorine adsorption by volcanic soils at Mt. Etna,Italy

Fluorine adsorption experiments were performed on 28 samples of the first 5 cm of topsoil collected on the flanks of Mt. Etna. The soil samples were equilibrated with F-rich rainwater (3.25 mg/L) at a soil/water weight ratio of 1/25. Aliquots of the supernatant were collected after 1, 7, 72, 720 and 5640 h and analysed for F content. The soil samples could be subdivided into three groups based on their F-adsorption behaviours after 1 h and at the end of the experiment: (1) negative adsorption (F released from the soil to the solution) after 1 h and negative or moderately positive adsorption at the end, (2) from negative after 1 h to strongly positive adsorption at the end, and (3) always strong positive adsorption. The adsorption capacity of the soils was positively correlated with the soil pH, the contents of finer granulometric fractions (clay and silt) and the weathering stage (as quantified by the chemical alteration index). The most F adsorbing soils are found at the periphery of the volcano where aquifers are more vulnerable to contamination due to the shallower depth of the water table. This study further evidences the importance of the Etnean soils in protecting groundwater from an excessive magmatic F input.     

Assessment of debris flow multiple-surge load model based on the physical process of debris-barrier interaction

Debris-flow impact load is one of the key parameters for design of engineering countermeasures. The multiple-surge load model is a remarkable progress in estimating the debris-flow impact load, which clearly delineates the contribution of each surge to the total impact load and the corresponding acting points. In order to better understand the impact process of channelized debris flow against flexible barrier, a series of medium-scale flume experiments with varying debris-flow volumetric solid concentration (0.40/0.50/0.55) were conducted. Especially, surge impact behavior is focused so that the predictability of the multiple-surge load model could be assessed. The flume and model flexible barrier were instrumented so that both the barrier dynamic response and the debris-flow properties (flow regime) could be correlated to facilitate the assessment. The results show that multiple-surge load model well predicts the total impact load. However, due to the simplification in the impact process, the interaction between the mobile phase (surge) and the deposited phase is ignored, resulting in discrepancy in the load distribution between the model prediction and experimental result. The remixing of deposited debris by the subsequent surges leads to downward momentum transfer to the lower section of barrier, which should be regarded as an adverse scenario of the design of flexible-barrier anchor capacity.

     

The nekhoroshev theorem and the asteroid belt dynamical system

The present paper reviews the Nekhoroshev theorem from the point of view of physicists and astronomers. We point out that Nekhoroshev result is strictly connected with the existence of a specific structure of the phase space, the existence of which can be checked with several numerical tools. This is true also for a degenerate system such as the one describing the motion of an asteroid in the so called main belt. The main difference is that in some parts of the belt, the Nekhoroshev result cannot apply a priori. Mean motion resonances of order smaller than the logarithm of the mass of Jupiter and first order secular resonances must be excluded. In the remaining parts, conversely, the Nekhoroshev theorem can be proved, provided someparameters, such as the masses, the eccentricities and the inclinations of the planets are small enough. At the light of this result, a massive campaign of numerical integrations of real and fictitious asteroids should allow to understand which is the real dynamical structure of the asteroid belt.     

On the origin of the faint-end of the red sequence in high-density environments

With the advent of the new generation wide-field cameras it became possible to survey in an unbiased mode galaxies spanning a variety of local densities, from the core of rich clusters, to compact and loose groups, down to filaments and voids. The sensitivity reached by these instruments allowed to extend the observation to dwarf galaxies, the most “fragile” objects in the universe. At the same time models and simulations have been tailored to quantify the different effects of the environment on the evolution of galaxies. Simulations, models, and observations consistently indicate that star-forming dwarf galaxies entering high-density environments for the first time can be rapidly stripped from their interstellar medium. The lack of gas quenches the activity of star formation, producing on timescales of \({\sim }\)1 Gyr quiescent galaxies with spectro-photometric, chemical, structural, and kinematical properties similar to those observed in dwarf early-type galaxies inhabiting rich clusters and loose groups. Simulations and observations consistently identify ram pressure stripping as the major effect responsible for the quenching of the star-formation activity in rich clusters. Gravitational interactions (galaxy harassment) can also be important in groups or in clusters whenever galaxies have been members since early epochs. The observation of clusters at different redshifts combined with the present high infalling rate of galaxies onto clusters indicate that the quenching of the star-formation activity in dwarf systems and the formation of the faint end of the red sequence is a very recent phenomenon.     

The notion of “distinguishability” between bulk elastic parameters on the basis of the Gibbs deformation energy

The present work aims in discussing a principle that distinguishes between elastic parameters sets, $ \{ \Upphi \} \equiv \{ K_{0} , \, K^{\prime}, \, V_{0} ,\ldots\} The present work aims in discussing a principle that distinguishes between elastic parameters sets, { \Upphi } o { K₀ ,  K^￠,  V₀ ,?} \{ \Upphi \} \equiv \{ K_{0} , \, K^{\prime}, \, V_{0} ,\ldots\} , on the basis of an energetic criterion: once a reference set, { \Upphi_R } \{ \Upphi_{R} \} , is given, another one can be fixed, { \Upphi _min } \left\{ {\Upphi_{ \min } } \right\} , so that they are as close as possible to each other, but yield non-equivalent deformation energy curves \Updelta G({ \Upphi } )_\textdeform \Updelta G(\{ \Upphi \} )_{\text{deform}} , i.e. they give \Updelta G({ \Upphi_R } )_\textdeform \Updelta G(\{ \Upphi_{R} \} )_{\text{deform}} and \Updelta G({ \Upphi _min } )_\textdeform \Updelta G(\{ \Upphi_{ \min } \} )_{\text{deform}} such that | \Updelta G({ \Upphi _min } )_\textdeform - \Updelta G({ \Upphi_R } )_\textdeform | 3 1×s[\Updelta G_\textdeform ]. \left| {\Updelta G(\{ \Upphi_{ \min } \} )_{\text{deform}} - \Updelta G(\{ \Upphi_{R} \} )_{\text{deform}} } \right| \ge 1\times \sigma [\Updelta G_{\text{deform}} ]. ΔG _deform, calculated using the equation of state (EoS), and its uncertainty σ[ΔG _deform], obtained by a propagation of the errors affecting { \Upphi } \{ \Upphi \} are crucial to fix which mineral assemblage forms at P–T conditions and allow one to assess the reliability of such a prediction. We explore some properties related to the principle introduced, using the average values of the elastic parameters found in literature and related uncertainties for di-octahedral mica, olivine, garnet and clinopyroxene. Two elementary applications are briefly discussed: the effect of refining V ₀ in fitting EoSs to P–V experimental data, in the case of garnet and omphacite, and the phengite 3T–2M ₁ relative stability, controlled by pressure.     

Trophic network model of the Northern Adriatic Sea: Analysis of an exploited and eutrophic ecosystem

A quantitative model of the trophic network of Northern Adriatic Sea marine ecosystem during the 1990s has been constructed, with the goal of analysing its trophic structure, identifying the key trophic groups and assessing the anthropogenic impacts on the ecosystem using the Ecopath modelling protocol. The Northern Adriatic Sea is an eutrophic, shallow basin, and one of the most heavily fished areas in the Mediterranean Sea. The network aggregation into discrete trophic levels sensu Lindeman shows that low trophic levels dominate biomass and energy flows, with 40% of the total system throughput flowing out from trophic level 2. Instead, upper trophic levels appear bottom-up controlled, highly depleted and not exerting any control on the trophic network, as shown by mixed trophic impact-based analyses. Microbial loop is comparable to grazing with respect to the magnitude of flows involved, as 66% of the trophic network flows originate from detritus, which is mainly consumed by bacteria. Key trophic groups are plankton groups, macro-crustaceans and detritus, and other r-selected organisms like squids and small pelagics, which have a great influence on the ecosystem. In particular, zooplankton acts as a bottleneck for energy flows, limiting the energy from the low trophic levels effectively reaching the upper food web. The high pelagic production caused by eutrophication sustains high fishery landings and impressive discard quantities, as well as the benthic compartment. Overall, the ecosystem appears quite productive and in a stressed and developmental status. Model results and comparisons with few existing historical data suggest that the low maturity and stressed state of the Northern Adriatic Sea are not only due to natural characteristics, but mainly to anthropogenic pressures.     

First <Superscript>13</Superscript>C/<Superscript>12</Superscript>C isotopic characterisation of volcanic plume CO<Subscript>2</Subscript>

We describe analytical details and uncertainty evaluation of a simple technique for the measurement of the carbon isotopic composition of CO₂ in volcanic plumes. Data collected at Solfatara and Vulcano, where plumes are fed by fumaroles which are accessible for direct sampling, were first used to validate the technique. For both volcanoes, the plume-derived carbon isotopic compositions are in good agreement with the fumarolic compositions, thus providing confidence on the method, and allowing its application at volcanoes where the volcanic component is inaccessible to direct sampling. As a notable example, we applied the same method to Mount Etna where we derived a δ¹³C of volcanic CO₂ between −0.9 ± 0.27‰ and −1.41 ± 0.27‰ (Bocca Nuova and Voragine craters). The comparison of our measurements to data reported in previous work highlights a temporal trend of systematic increase of δ¹³C values of Etna CO₂ from ~ −4‰, in the 1970’s and the 1980’s, to ~ −1‰ at the present time (2009). This shift toward more positive δ¹³C values matches a concurrent change in magma composition and an increase in the eruption frequency and energy. We discuss such variations in terms of two possible processes: magma carbonate assimilation and carbon isotopic fractionation due to magma degassing along the Etna plumbing system. Finally, our results highlight potential of systematic measurements of the carbon isotopic composition of the CO₂ emitted by volcanic plumes for a better understanding of volcanic processes and for improved surveillance of volcanic activity.     

Geological evidence for strong historical earthquakes in an “aseismic” region: The Pollino case (Southern Italy)

The Pollino Range is the southernmost segment of the Southern Apennines at the boundary with the Calabrian Arc. While several strong earthquakes (magnitude 6.5–7.0) have occurred in nearby regions, the Pollino area has no known historical record of seismic events of magnitude > 5. We carried out an aerial photograph interpretation and a field survey of the Pollino fault (the major Quaternary normal fault of the area) in order to characterize geologically the seismic potential of this structure. We dug two sets of trenches across fault scarps within the apecies of latest Pleistocene to Holocene alluvial fans at the Masseria Quercia Marina (MQM) and Grotta Carbone (GC) sites, in the central segment of the southern Pollino Range front. At both sites we identified two surface faulting events affecting the alluvial fan deposits and two overlying colluvial units of historical age. The penultimate event produced a vertical offset of 80–90 cm at GC and 50–60 cm at MQM; while the last event produced a vertical offset of 40–50 cm at GC and few centimeters of offset at MQM. Detailed geomorphological field observations suggest that the two historical earthquakes reactivated the entire length of the Masseria Marzano-Civita segment of the Pollino fault (rupture length about 18 km). For events in this range of rupture length and vertical displacement, comparison with surface faulting earthquakes in the Apennines (and abroad) indicates a magnitude of 6.5–7.0. Therefore, the maximum potential earthquake and the seismic hazard of the Pollino area are significantly larger than that suggested by the available historical seismic catalogue.