Isostasy and paleotemperatures in the Southern Tyrrhenian Basin,Mediterranean Sea

The present-day basement depth of the seafloor in the absence of sediment loading was inferred along a traverse crossing the Southern Tyrrhenian Basin. A correction for sediment loading was proposed on the basis of density, seismic velocity and porosity data from selected deep boreholes. The empirical relation between sediment correction and seismic two-way travel time was extrapolated downward by applying the Nafe–Drake curve and a specific porosity–depth relation. The sediment loading response of the basement calculated for flexural isostasy is on average about one hundred meters lower than results for local isostasy. A pure lithosphere extensional model was then used to predict quantitatively the basement subsidence pattern on the margins of the basin. The basement depth is consistent with uniform extension model predictions only in some parts of the margins. The observed variability in the region of greatest thinning (transition from continental to oceanic crust) is attributable to the weakening effect caused by diffuse igneous intrusions. Subsidence of the volcanic Calabrian–Sicilian margin is partly accounted for by magmatic underplating. The comparison of the calculated subsidence with an oceanic lithosphere cooling model shows that subsidence is variable in some areas, particularly in the Marsili Basin. This argues for a typical back-arc origin for the Tyrrhenian Basin, as a result of subduction processes. By taking into account the geodynamic setting, stratigraphic data from the deepest hole and the terrestrial heat flow, we reconstructed the paleotemperatures of cover sediments. The results suggest that low temperatures generally have prevailed during sediment deposition and that the degree of maturation is expected not to be sufficient for oil generation processes.     

New records of cold‐water coral sites and fish fauna characterization of a potential network existing in the Mediterranean Sea

New cold‐water coral (CWC) sites were recorded along the Apulian margin (Central Mediterranean). The species composition and depth distribution of CWCs were updated. A distribution of the CWC sites coincident with the course of the dense‐water masses that flow between the Southern Adriatic and Northern Ionian was confirmed. The faunal assemblages of five of these CWC sites were investigated and compared using experimental longlines during the spring–summer and autumn–winter seasons, between 2010 and 2014. Differences in ecological variables amongst the sites in each season were evaluated by means of a set of univariate and multivariate methods (analysis of variance, permutational multivariate analysis of variance, non‐metric multidimensional scaling). Although some differences were detected in relation to the different depths examined during spring–summer, the CWC sites showed similar features in terms of species richness and diversity as well as in the abundance of the same fish species (Galeus melastomus, Conger conger, Helicolenus dactylopterus, Merluccius merluccius, Phycis blennoides and Pagellus bogaraveo) most probably because of the distribution of adult specimens in structurally complex and heterogeneous habitats, which act as a potential ‘refuge network’ with respect to commercial fishing. The presence of maturing and mature individuals as well as post‐reproductive females indicates that these CWC sites also act as spawning areas, representing a potential ‘renewal network’ for the fish populations. The term ‘network’ used here refers to several similar subsystems (CWC sites) that play the same ecological role in a wider system (Apulian margin). These CWC communities need coherent conservation measures and management strategies according to the Ecosystem Approach to Fisheries.     

Chemistry and sulfur isotopic composition of precipitation at Bologna, Italy

Individual and monthly precipitation samples from the polluted atmosphere of Bologna (Emilia-Romagna province) were collected during March 1996 to May 1997 and analyzed for major ions in solution and S isotopes in dissolved SO₄.Weighted mean enrichment factors relative to seawater are found to be 1.0 for Na, 15.2 for K, 105 for Ca, 3.3 for Mg, 17.3 for SO₄ and 663 for HCO⁻₃. Very good positive correlations are observed for the Ca²⁺–Mg²⁺–HCO⁻₃–SO²⁻₄–NO⁻₃ system, indicating that dissolution of Ca (±Mg)-carbonate particles by H₂SO₄ and HNO₃ from combustion of oil and gas is a major process controlling the chemical composition of rain and snow. Na⁺ and Cl⁻ in monthly precipitation derive essentially from sea spray, but the contribution of Na⁺ from continental sources is appreciable in a number of individual rains. NH⁺₄ appears to be on average more abundant in spring and summer precipitation, its main sources being microbial activity in soils and application of fertilizers. K⁺ is probably of continental origin from soil dust.The S isotopic composition of SO₄ is systematically positive, with mean δ³⁴S values of +3.2±1.6‰ (n=40) in individual precipitation and +2.8±1.4‰ (n=12) in monthly precipitation. These isotopic compositions are interpreted in terms of a dominant contribution of S from anthropogenic emissions and subordinate contributions from biogenic and marine sources. Pollutant SO₄ is estimated to have a δ³⁴S value in the range +2.5 to +4.5‰, whereas a distinctive δ³⁴S of −4.5‰ or lower indicates SO₄ from oxidation of biogenic gases.The isotopic and chemical compositions of SO₄ do not depend on wind direction, thus testifying to a mostly local source for pollutant S in the Bologna atmosphere.     

Real-time estimation of hazard for landslides triggered by rainfall

 Landslide movements triggered by rainfall can be foreseen in real-time by modelling the relationship between rainfall amount and landslide occurrence. This paper deals with the problem of the reliability of the FLaIR (Forecasting of Landslides Induced by Rainfalls) model when applied to forecasting landslide movements in the usual condition of poor historical information availability. In this case, the identification of the admissibility field for the model parameters, instead of a point estimation, leads to an improvement of the forecasting reliability. Moreover, this approach makes the model capable of taking into account information embodied in periods of heavy rain but without movement. The concepts of informative content and foreseeability of landslide movements are introduced and their duality is analyzed. The effectiveness of the estimation procedure described has been tested by application on two landslides located in southern Italy. Received: 15 October 1996 · Accepted: 25 June 1997     

Exploration of the high-redshift universe enabled by THESEUS

Experimental Astronomy - At peak, long-duration gamma-ray bursts are the most luminous sources of electromagnetic radiation known. Since their progenitors are massive stars, they provide a tracer...     

3D tomographic imaging of the southern Apennines (Italy): A statistical approach to estimate the model uncertainty and resolution

A new dataset of first P-wave arrival times is used to derive the 3D tomographic model of the Campania-Lucania region in the southern Apennines (Italy). We address the issue related to the non-uniqueness of the tomographic inversion solution through massive numerical experimentation based on the global exploration of the model parameter space starting from a large variety of physically plausible initial models. The average of all the realizations is adopted as the best-fit solution and the uncertainty of the model parameters is studied using a statistical approach based on a Monte Carlo-type analysis. How the uncertainty in the initial model, earthquake locations, and data influences the inversion result is studied by considering separately the individual effects. Checkerboard tests are performed to estimate the resolving power of the dataset. Re-located seismicity in a reliable new 3D tomographic model allows us to correlate the earthquake distribution with the main seismogenic structures present in the area.     

Modelling the rainfall-induced mobilization of a large slope movement in northern Calabria

Two recent phases of mobilization of a large, rainfall-induced debris slide are analysed in terms of relationships between rains and phases of displacement. The first activation at San Rocco (San Benedetto Ullano, Calabria) occurred on 28 January 2009, after extraordinary rains had stricken the region for a couple of months. Detailed geomorphologic field surveys, combined with measurements of superficial displacements at datum points, were performed to properly recognize the evolution of the phenomenon. In addition, a real-time control system of rains and superficial displacements measured at extensometers was implemented, to better analyse the evolution of the phenomenon. In early May 2009, the activity reduced to very slow displacements, persisting in the same condition for the following 8 months. On 1 February 2010, premonitory signs of a new phase of activation were noticed, again following 2 months of extraordinary rainfalls. After few days of further precipitations, the middle sector of the landslide activated since 11 February, disrupting the road network and threatening the major lifelines and some buildings. A hydrological analysis aimed at simulating the dates of activation and the main phases of acceleration of the phenomenon was carried out, by calibrating the empirical model FLaIR against the daily rainfalls and the history of known phases of mobilization since 1970. Calibration allowed to successfully simulate both the cited phases of activity of the San Rocco landslide, by predicting the beginning of the movements as well as the following paroxysmal stages, as testified by the measurements at datum points and extensometers. The set of parameters obtained through calibration reflects the influence of both prolonged antecedent rains, and of high-intensity rainfalls of shorter duration, which slightly preceded the major displacements. Once calibrated the model, a suitable threshold could be defined, by analysing the trend of the mobility function against the history of activations of the considered slope movement, and by excluding false alarms. Accordingly, a reliable tool for predicting the phases of activity of a large slope movement could therefore be obtained.     

Application of a newN-body code to the encounters of galaxies and dissipationless formation of elliptical galaxies

A new code has been used to simulate the formation of elliptical galaxies via a dissipationless collapse by a numerical experiment. Preliminary results of numerical simulations are presented for initial 2T/|W| conditions ranging from 10^–2 to 10^–5. The importance of inhomogeneity in the initial density distribution and of merging is outlined.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

The maximum momentum of particles accelerated at cosmic ray modified shocks

Particle acceleration at non-relativistic shocks can be very efficient, leading to the appearance of non-linear effects due to the dynamical reaction of the accelerated particles on the shock structure and to the non-linear amplification of the magnetic field in the shock vicinity. The value of the maximum momentum, p _max, in these circumstances cannot be estimated using the classical results obtained within the framework of test-particle approaches. We provide here the first attempt at estimating p _max in the cosmic ray modified regime, taking into account the non-linear effects mentioned above.