The deep seismicity of the Tyrrhenian Sea is analysed using data from a new instrumental catalogue of the seismicity of the Italian area. We use algorithms for the determination of absolute and relative hypocentral locations and for the evaluation of the geometry and coherence of the state of stress within the subducting slab. The structure of the Benioff zone, although simpler than previously indicated, reveals anomalous traits both in the seismicity distribution and in the stress geometry, confirming that standard subduction models cannot be applied in the Tyrrhenian region. The velocity anomaly and the location of few isolated events indicate that the subducted slabs extend to the north along the Apenninic chain approximately to the latitude of the Irpinia region, in Central Italy (? 42°N). 相似文献
Optical fibre–based sensors have now established their place in the field of geohazard monitoring due to their sensitivity to strain and temperature changes. Progressive development in the technology leads to the availability of novel, accurate and durable sensors at a relatively limited cost. This creates room for original monitoring applications that have been, so far, impeded by the shortcomings of conventional monitoring tools. In this work, we explore the applicability of an interferometric optical fibre sensor as a vibration sensing tool at laboratory scale. We tested the ability of the sensor to identify precursors of instability in a downscaled model of a rainfall-induced landslide composed of granular material. We carried out four experimental tests which involved different sensor deployments and soil mixtures. The recorded signals were processed by means of a time–frequency analysis and we identified two frequency-domain parameters—the spectral centroid and band power—that could provide information on the development of instability. Their ratio yielded a unique parameter through which a precursory stage could be outlined by defining a threshold value based on the data collected at the beginning of the experiment. In our lab tests, precursors of instability were detected 2–3 min before a crack was observed at the surface. This may upscale to a lead time of about 20–30 min or more in the field, classifying our monitoring approach in between an alarm and a warning system. The work presented here can be considered a first promising step towards an innovative monitoring system and shows the potential of optical fibre sensing as a shallow landslide monitoring technique, encouraging further testing, especially in real-case studies.
This project was carried out to assess the levels and spatial distribution of organochlorine compounds in the coastal marine environment, using mussels as bioindicators to evaluate the coastal water quality. Levels of polychlorobiphenils (PCB), chlorinated pesticides (DDT isomers, HCH isomers, Aldrin, Dieldrin, alfa-Endosulfan, Hexachlorobenzene, Pentachlorobenzene) and polybrominated diphenyl ethers (PBDEs) were determined in tissues from mussels (Mytilus galloprovincialis) collected along the Apulia Region coasts (Mediterranean Sea). Results indicate that contamination by organochlorine compounds is higher in mussels sampled in the Ionian Sea than in those from the Adriatic Sea, with PCB levels up to seven times higher in mussels from Ionian than from the Adriatic Sea. Although PCB levels were above the maximum values indicated by both European Community (EC) and National regulation in several sample sites, the PCB concentrations were particularly high in some stations, suggesting that these locations require a much specific attention. Conversely, results on the mussel contamination by PBDEs highlight their ubiquitous environmental distribution, and underline the need to establish the maximum level for these compounds in foodstuff, according to European Regulations. 相似文献
A novel semi-analytic spectral method, based on eigenfunction expansions, is applied to model the angular momentum transport in stellar radiative interiors. The advantages of our approach are shown by applying it to a spin-down model for a 1M⊙ main-sequence star. The evolution of the coupling between core and envelope is investigated for different values of the viscosity and different geometries and intensities of the poloidal field. We suggest that a quadrupolar poloidal field may explain the short coupling timescale (τc～10 Myr) needed to reproduce the observed rotational evolution of fast rotators on the zero age main sequence, while a dipolar geometry is indicated in the case of slow rotators (τc～100 Myr). Our method provides a rigorous analytic treatment of a classic MHD problem and allows us to explore the influence of various parameters on the rotational history of radiative interiors. 相似文献
Monte Carlo analysis is a statistical simulation method that is often used to assess and quantify the outcome variance in
complex environmental fate and effects models. Total outcome variance of these models is a function of (1) the variance (uncertainty
and/or variability) associated with each model input and (2) the sensitivity of the model outcome to changes in the inputs.
To propagate variance through a model using Monte Carlo techniques, each variable must be assigned a probability distribution.
The validity of these distributions directly influences the accuracy and reliability of the model outcome. To efficiently
allocate resources for constructing distributions one should first identify the most influential set of variables in the model.
Although existing sensitivity and uncertainty analysis methods can provide a relative ranking of the importance of model inputs,
they fail to identify the minimum set of stochastic inputs necessary to sufficiently characterize the outcome variance. In
this paper, we describe and demonstrate a novel sensitivity/uncertainty analysis method for assessing the importance of each
variable in a multimedia environmental fate model. Our analyses show that for a given scenario, a relatively small number
of input variables influence the central tendency of the model and an even smaller set determines the spread of the outcome
distribution. For each input, the level of influence depends on the scenario under consideration. This information is useful
for developing site specific models and improving our understanding of the processes that have the greatest influence on the
variance in outcomes from multimedia models. 相似文献
Persistent organochlorines, such as polychlorinated biphenyls, including coplanar congeners and DDT compounds, were measured in the liver of a teleost species: namely, Lophius budegassa. The mean concentrations of PCBs (1249 ng/g wet wt) were comparable with DDTs mean levels (1459 ng/g wet wt). Among DDTs the compound found at the highest concentration was p,p'-DDE representing 76% of the total DDT burden. The PCB profiles were dominated by congeners 153, 180, and 138 accounting for 49.8%, 16.0% and 13.7% of the total PCBs. The total 2,3,7,8-TCDD toxic equivalent (TEQs) of six coplanar PCBs, including mono- and non-ortho congeners, was 0.98 pg/g wet wt. The congeners with highest TEQs values were non-ortho-congeners followed by mono-ortho ones. 相似文献
