A Comparison of Data‐Driven Groundwater Vulnerability Assessment Methods     

Alessandro Sorichetta  Cristiano Ballabio  Marco Masetti  Gilpin R. Robinson Jr.  Simone Sterlacchini 《Ground water》2013,51(6):866-879

Increasing availability of geo‐environmental data has promoted the use of statistical methods to assess groundwater vulnerability. Nitrate is a widespread anthropogenic contaminant in groundwater and its occurrence can be used to identify aquifer settings vulnerable to contamination. In this study, multivariate Weights of Evidence (WofE) and Logistic Regression (LR) methods, where the response variable is binary, were used to evaluate the role and importance of a number of explanatory variables associated with nitrate sources and occurrence in groundwater in the Milan District (central part of the Po Plain, Italy). The results of these models have been used to map the spatial variation of groundwater vulnerability to nitrate in the region, and we compare the similarities and differences of their spatial patterns and associated explanatory variables. We modify the standard WofE method used in previous groundwater vulnerability studies to a form analogous to that used in LR; this provides a framework to compare the results of both models and reduces the effect of sampling bias on the results of the standard WofE model. In addition, a nonlinear Generalized Additive Model has been used to extend the LR analysis. Both approaches improved discrimination of the standard WofE and LR models, as measured by the c‐statistic. Groundwater vulnerability probability outputs, based on rank‐order classification of the respective model results, were similar in spatial patterns and identified similar strong explanatory variables associated with nitrate source (population density as a proxy for sewage systems and septic sources) and nitrate occurrence (groundwater depth).  相似文献   

Frictional Properties of a Low-Angle Normal Fault Under In Situ Conditions: Thermally-Activated Velocity Weakening     

André R. Niemeijer  Cristiano Collettini 《Pure and Applied Geophysics》2014,171(10):2641-2664

The Zuccale fault is a regional, low-angle, normal fault, exposed on the Isle of Elba in central Italy that accommodated a total shear displacement of 6–8 km. The fault zone structure and fault rocks formed at <8 km crustal depth. The present-day fault structure is the final product of several deformation processes superposed during the fault history. In this study, we report results from a series of rotary shear experiments performed on 1-mm thick powdered gouges made from several fault rock types obtained from the Zuccale fault. The tests were done under conditions ranging from room temperature to in situ conditions (i.e., at temperatures up to 300 °C, applied normal stresses up to 150 MPa, and fluid-saturated.) The ratio of fluid pressure to normal stress was held constant at either λ = 0.4 or λ = 0.8 to simulate an overpressurized fault. The samples were sheared at a constant sliding velocity of 10 μm/s for at least 5 mm, after which a velocity-stepping sequence from 1 to 300 μm/s was started to determine the velocity dependence of friction. This can be represented by the rate-and-state parameter (a–b), which was determined by an inversion of the data to the rate-and-state equations. Friction of the various fault rocks varies between 0.3 and 0.8, similar to values obtained in previous studies, and decreases with increasing phyllosilicate content. Friction decreases mildly with temperature, whereas normal stress and fluid pressure do not affect friction values systematically. All samples exhibited velocity strengthening, conditionally stable behavior under room temperature conditions and (a–b) increased with increasing sliding velocity. In contrast, velocity weakening, accompanied by stick–slips, was observed for the strongest samples at 300 °C and sliding velocities below 10 μm/s. An increase in fluid pressure under these conditions led to a further reduction in (a–b) for all samples, so that they exhibited unstable, stick–slip behavior at low sliding velocity. The results suggest that phyllosilicate-bearing fault rocks can deform by stable, aseismic creep at low, resolved shear stress and low shear rate conditions. An increase in fluid pressure or loading of stronger portions could lead to a runaway instability. The runaway instability might be limited in size because of (1) the fault heterogeneity, (2) the observed strengthening at higher sliding velocities, and (3) a co-seismic drop in pore-fluid pressure.  相似文献   

The real-space clustering of luminous red galaxies around z < 0.6 quasars in the Sloan Digital Sky Survey     

Nikhil Padmanabhan †  Martin White  Peder Norberg  Cristiano Porciani 《Monthly notices of the Royal Astronomical Society》2009,397(4):1862-1875

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The Diamantina Monazite: A New Low‐Th Reference Material for Microanalysis          下载免费PDF全文

Guilherme O. Gonçalves  Cristiano Lana  Ricardo Scholz  Ian S. Buick  Axel Gerdes  Sandra L. Kamo  Fernando Corfu  Daniela Rubatto  Michael Wiedenbeck  Hermínio A. Nalini Jr.  Luiz Carlos A. Oliveira 《Geostandards and Geoanalytical Research》2018,42(1):25-47

Most monazite reference materials (RMs) for in situ U‐Pb geochronology are rich in Th; however, many hydrothermal ore deposits contain monazite that is low in trace element contents, including Th, U and Pb. Because of potential problems with matrix effects and the lack of appropriate matrix‐matched RMs, such variations can bias dating of hydrothermal deposits. In this paper, we describe a polycrystalline low‐U and low‐Th Diamantina monazite from the Espinhaço Range, SE Brazil. It has a U‐Pb ID‐TIMS weighted mean ²⁰⁷Pb^*/²³⁵U ratio of 0.62913 ± 0.00079, ²⁰⁶Pb^*/²³⁸U of 0.079861 ± 0.000088 and ²⁰⁷Pb^*/²⁰⁶Pb^* of 0.057130 ± 0.000031, yielding a weighted mean ²⁰⁶Pb^*/²³⁸U date of 495.26 ± 0.54 Ma (95% c.l.). In situ dates acquired with different methods (LA‐(Q, SF, MC)‐ICP‐MS and SIMS) are within uncertainty of the ID‐TIMS data. U‐Pb LA‐(Q, MC)‐ICP‐MS runs, using Diamantina as a primary RM, reproduced the ages of other established RMs within < 1% deviation. The LA‐MC‐ICP‐MS analyses yielded homogeneous Sm‐Nd isotopic compositions (¹⁴³Nd/¹⁴⁴Nd = 0.511427 ± 23, 2s; ¹⁴⁷Sm/¹⁴⁴Nd = 0.1177 ± 13, 2s) and εNd_(495 Ma) of ?18.7 ± 0.5 (2s). SIMS oxygen isotope determinations showed measurement reproducibility better than ± 0.3‰ (2s), confirming Diamantina's relative homogeneity at test portion masses below 1 ng.  相似文献   

U-Pb Saturn: New U-Pb/Pb-Pb Data Reduction Software for LA-ICP-MS     

Joao P.A. Silva  Cristiano Lana  Ariela Mazoz  Ian Buick  Ricardo Scholz 《Geostandards and Geoanalytical Research》2023,47(1):49-66

U-Pb Saturn is new freeware for U-Pb LA-ICP-MS data reduction. It has been developed to provide easy interaction with and visualisation of LA-ICP-MS U-Pb datasets, and allows fast and reliable data reduction of hundreds of data-points. Saturn offers dynamic graphic interfaces to quickly view, evaluate, and plot U-Pb and Pb-Pb isotope data. It operates online (or offline), giving the freedom to change parameters and reprocess data at any stage of data acquisition. The main interface allows the user to: (1) choose the best statistics for drift correction, (2) include/exclude offset factors and (3) apply (or not) Pb_c corrections in different modes. Signal intensities are displayed in a separate graphic interface that allows users to interact with the time-resolved signal of individual spot analyses. All graphic windows are interactive; any modification to data treatment (e.g., inclusion or exclusion of analyses of reference material, or modification of the time-resolved signal windows) is instantaneously updated on the data tables. Saturn is particularly attractive for beginners in LA-ICP-MS U-Pb geochronology as it is non-commercial, easy to install, and very interactive. Coding information and a version of the software can be accessed at http://www.air.ufop.br .  相似文献   

Two ways of biasing galaxy formation     

Paolo Catelan  Cristiano Porciani  Marc Kamionkowski 《Monthly notices of the Royal Astronomical Society》2000,318(3):L39-L44

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Landslide susceptibility mapping by remote sensing and geomorphological data: case studies on the Sorrentina Peninsula (Southern Italy)     

Claudia Spinetti  Marina Bisson  Cristiano Tolomei  Laura Colini  Alessandro Galvani  Marco Moro 《地理信息系统科学与遥感》2019,56(6):940-965

The Sorrentina Peninsula is a densely populated area with high touristic impact. It is located in a morphologically complex zone of Southern Italy frequently affected by dangerous and calamitous landslides. This work contributes to the prevention of such natural disasters by applying a GIS-based interdisciplinary approach aimed to map the areas more potentially prone to trigger slope instability phenomena. We have developed the Landslide Susceptibility Index (LSI) combining five weighted and ranked susceptibility parameters on a GIS platform. These parameters are recognized in the literature as the main predisposing factors for triggering landslides. This work combines analyses conducted on Remote Sensing, Geo-Lithology and Morphometry data and it is organized in the following logical steps: i) Multi-temporal InSAR technique was applied to Envisat-ASAR (2003–2010) and COSMO-SkyMed (2013–2015) datasets to obtain the ground displacement time series and the relative mean ground velocity maps. InSAR allowed the detection of the areas that are subjected to ground deformation and the main affected municipalities; ii) Such deformation areas were investigated through airborne photo interpretation to identify the presence of geomorphological peculiarities connected to potential slope instability. Subsequently, some of these peculiarities were checked on the field; iii) In these deformation areas the susceptibility parameters were mapped in the entire territory of Amalfi and Conca dei Marini and then investigated with a multivariate analysis to derive the classes and the respective weights used in the LSI calculation. The resulting LSI map classifies the two municipalities with high spatial resolution (2m) according to five classes of instability. The map highlights that the high/very high susceptibility zones cover 6% of the investigated territory and correspond to potential landslide source areas characterized by 25°-70° slope angles. A spatial analysis between the map of the historical landslides and the areas classified according to susceptibility allowed testing of the reliability of the LSI Index, resulting in 85% prediction accuracy.  相似文献   

Tourmaline composition and boron isotopes record lateritic weathering during the Great Oxidation Event     

Alexandre Raphael Cabral  Tiago Henrique DeFerreira  Cristiano Lana  Marco P. de Castro  Glucia Queiroga 《地学学报》2021,33(1):46-55

Identifying evidence of oxidative weathering in the geological record is essential to trace the evolution of Earth's atmosphere oxygenation. Metamorphosed residues of lateritic weathering have been identified as two rock types in the 2.1‐Ga‐old Cercadinho Formation, Piracicaba Group, Quadrilátero Ferrífero of Minas Gerais. One is tourmaline–hematite–sillimanite–kyanite quartzite; the other is rutile–tourmaline–hematite–muscovite phyllite. Both rocks have abundant tourmaline with δ¹¹B values between about ?17‰ and ?13‰. The Cercadinho tourmaline is roughly parallel to the povondraite–“oxy‐dravite” join of meta‐evaporitic tourmaline, in its more aluminous segment, offset to higher contents of iron. These compositional and isotopic characteristics of the Cercadinho tourmaline indicate that continental evaporitic brines interacted with aluminium‐ and iron‐rich residues of lateritic weathering. The abundance of disseminated tourmaline, a mineral poorly reported from palaeosols worldwide, implies a boron‐rich brine overprint on the lateritic profile before the onset of metamorphism, reflecting a climatic change from humid to arid conditions in a continental setting. The recognition of lateritic weathering in the Cercadinho Formation contributes to the amount of evidence for increased levels of atmospheric oxygen between 2.22 and 2.06 Ga ago.  相似文献   

Toward semantics-aware annotation and retrieval of spatial data     

Cristiano Fugazza 《Earth Science Informatics》2011,4(4):225-239

The retrieval of spatial resources is typically hindered by the lack of exhaustive metadata, linguistic issues, multilingualism, and domain-related terminology mismatches. This paper describes an experimental attempt to set up a knowledge base that will serve as groundwork for harmonising domain knowledge from distinct thematic areas, to enable the semantics-aware annotation of resources, and to support the implementation of novel discovery techniques. Setting this up also required establishing a general work flow for translating ISO-compliant registries into SKOS/RDF data structures and enriching them with structural information. These steps are also presented. The validity of the approach is then evaluated by analysing various applications’ exploitation of the knowledge base in diverse use cases.  相似文献   

Luminosity- and redshift-dependent quasar clustering     

Cristiano Porciani  Peder Norberg 《Monthly notices of the Royal Astronomical Society》2006,371(4):1824-1834

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