Kriging with external drift in a Birnbaum–Saunders geostatistical model

Spatial models to describe dependent georeferenced data are applied in different fields and, particularly, are used to analyze earth and environmental data. Most of these applications are carried out under Gaussian spatial models. The Birnbaum–Saunders distribution is a unimodal and positively skewed model which has received considerable attention in several areas, including earth and environmental sciences. In addition, theoretical arguments have been provided to justify its usage in the data modeling from these sciences, at least in the same settings where the lognormal distribution can be employed. This paper presents kriging with external drift based on a Birnbaum–Saunders spatial model. The maximum likelihood method is considered to estimate its parameters. The results obtained in the paper are illustrated by an experimental data set related to agricultural management. Specifically, in this illustration, the spatial variability of magnesium content in the soil as a function of calcium content is analyzed.     

Geolithological and anthropogenic controls on the hydrochemistry of the Volturno river (Southern Italy)

The present work aims to study the main chemical and physical water parameters in the upper and middle Volturno river catchment (southern Italy), between the Capo Volturno springs and the confluence with the Calore river. This study makes use of morphology, geolithology, tectonic, land use, and physico‐chemical (pH, electrical conductivity, redox potential, temperature, major ions, and ²²²Rn) data for the identification of the main sources of surface and groundwaters in the Volturno catchment and of their evolution and mixing both in base flow and peak flow conditions. The study was also performed to assess whether the alteration due to potential anthropogenic contamination may hamper the identification of natural “primitive” sources of surface waters, especially in the populated and farmed plains far from the river headwaters. Our data suggest that water chemistry of this stretch of the Volturno river is dominated mainly by lithology and, only marginally, by the intense exogenous activities and that this trend is appreciable in both base flow and peak flow conditions. The proposed simple geochemical approach based on easy‐to‐sample matrices and on cost‐effective standard methods is a valuable tool to address catchment functionality especially in upland areas, where complex geologic and structural settings, heterogeneous groundwater flow, and logistical issues are the rule rather than the exception. Because the upper and middle Volturno catchment is comparable with numerous valleys of the Mediterranean area, this study could be a reference for analogous applications.     

A statistical approach to crowdsourced smartphone-based earthquake early warning systems

The Earthquake Network research project implements a crowdsourced earthquake early warning system based on smartphones. Smartphones, which are made available by the global population, exploit the Internet connection to report a signal to a central server every time a vibration is detected by the on-board accelerometer sensor. This paper introduces a statistical approach for the detection of earthquakes from the data coming from the network of smartphones. The approach allows to handle a dynamic network in which the number of active nodes constantly changes and where nodes are heterogeneous in terms of sensor sensibility and transmission delay. Additionally, the approach allows to keep the probability of false alarm under control. The statistical approach is applied to the data collected by three subnetworks related to the cities of Santiago (Chile), Iquique (Chile) and Kathmandu (Nepal). The detection capabilities of the approach are discussed in terms of earthquake magnitude and detection delay. A simulation study is carried out in order to link the probability of detection and the detection delay to the behaviour of the network under an earthquake event.     

An analysis of the scalar geodetic boundary-value problem with natural regularity results

A new local existence and uniqueness theorem is obtained for the scalar geodetic boundary-value problem in spherical coordinates. The regularities H _α and H _1+α are assumed for the boundary data g (gravity) and v (gravitational potential) respectively. Received: 27 July 1998 / Accepted: 19 April 1999     

三维虚拟动画模拟食鱼古魔翼龙Kellner & Tomida, 2000 (翼龙目, 翼手龙亚目)的站姿生物力学

Pterosaurs, usually known as flying reptiles, were the first vertebrate group to develop active flight. Despite being studied for more than 200 years, there are still many controversial questions regarding pterosaur functional morphology, such as the stance and gait when grounded, which rely primarily on direct examination of well-preserved articulated specimens, ichnofossils (trackways) and phylogenetic inferences.     

Surface electrical resistivity tomography and hydrogeological characterization to constrain groundwater flow modeling in an agricultural field site near Ferrara (Italy)

A portion of an unconfined alluvial aquifer located in the Padana Plain (Italy) was characterized following an integrated hydro-geophysical approach. Initially an electrical resistivity tomography (ERT) survey was employed to localize the boundaries of a modest paleo-channel body and to design the installation of a groundwater monitoring network. Multilevel slug-tests were performed to estimate the aquifer’s saturated hydraulic conductivities. Determined permeability values together with electrical resistivity data were correlated. The correlation resulted in a site specific bi-logarithmic linear relationship. Based on this relationship, punctually determined hydraulic conductivities were spatially extended over the studied flow domain. Finally, continuously measured piezometric heads were used to calibrate a 3D flow model. Sensitivity analysis was performed to confirm the reliability of the reconstructed permeability field, as well as, to assess the minimum number of direct measurements needed to safely characterize the selected aquifer portion. The integration of the ERT survey results with the classical hydrogeological tests can be conveniently applied to constrain the permeability field during flow model calibration. Although the applicability of the determined relationship is site specific, the followed procedure is useful especially when there is a need to optimize the available resources and in case of small-scale pilot studies.     

A Europe–South America network for climate change assessment and impact studies

The goal of the CLARIS project was to build an integrated European–South American network dedicated to promote common research strategies to observe and predict climate changes and their consequent socio-economic impacts taking into account the climate and societal peculiarities of South America. Reaching that goal placed the present network as a privileged advisor to contribute to the design of adaptation strategies in a region strongly affected by and dependent on climate variability (e.g. agriculture, health, hydro-electricity). Building the CLARIS network required fulfilling the following three objectives: (1) The first objective of CLARIS was to set up and favour the technical transfer and expertise in earth system and regional climate modelling between Europe and South America together with the providing of a list of climate data (observed and simulated) required for model validations; (2) The second objective of CLARIS was to facilitate the exchange of observed and simulated climate data between the climate research groups and to create a South American high-quality climate database for studies in extreme events and long-term climate trends; (3) Finally, the third objective of CLARIS was to strengthen the communication between climate researchers and stakeholders, and to demonstrate the feasibility of using climate information in the decision-making process.     

Asteroid photometric and polarimetric phase curves: Joint linear‐exponential modeling

Abstract— We present Markov‐Chain Monte‐Carlo methods (MCMC) for the derivation of empirical model parameters for photometric and polarimetric phase curves of asteroids. Here we model the two phase curves jointly at phase angles ≤25° using a linear‐exponential model, accounting for the opposition effect in disk‐integrated brightness and the negative branch in the degree of linear polarization. We apply the MCMC methods to V‐band phase curves of asteroids 419 Aurelia (taxonomic class F), 24 Themis (C), 1 Ceres (G), 20 Massalia (S), 55 Pandora (M), and 64 Angelina (E). We show that the photometric and polarimetric phase curves can be described using a common nonlinear parameter for the angular widths of the opposition effect and negative‐polarization branch, thus supporting the hypothesis of common physical mechanisms being responsible for the phenomena. Furthermore, incorporating polarimetric observations removes the indeterminacy of the opposition effect for 1 Ceres. We unveil a trend in the interrelation between the enhancement factor of the opposition effect and the angular width: the enhancement factor decreases with decreasing angular width. The minimum polarization and the polarimetric slope at the inversion angle show systematic trends when plotted against the angular width and the normalized photometric slope parameter. Our new approach allows improved analyses of possible similarities and differences among asteroidal surfaces.     

Quantitative analysis of extensional joints in the southern Adriatic foreland (Italy), and the active tectonics of the Apulia region

The Adriatic foreland of the Apennines comes ashore only in Apulia (easternmost Italy). Its southern part, our study area, lacks any structural analysis devoted to define its recent-to-active tectonics. Throughout the Quaternary, this region was affected by mild brittle deformation with rare faults, characterized by small displacement, and widespread extension joints, frequently organized in sets. Therefore, we conducted a quantitative and systematic analysis of the joint sets affecting Quaternary deposits, by applying an inversion technique ad hoc to infer the orientation and ratio of the principal stress axes, R = (σ₂ ? σ₃)/(σ₁ ? σ₃). Within a general extensional regime, we recognized three deformational events of regional significance. The oldest event, constrained to the early and middle part of the Middle Pleistocene, is characterized by variable direction of extension and R between 0.64 and 0.99. The penultimate event, dated late Middle Pleistocene, is characterized by an almost uniaxial tension, with a horizontal σ₃ striking ～N43°E; R is high, between 0.85 and 0.99. The most recent event is characterized by the lowermost R values, that never exceed 0.47 and are frequently <0.30, indicating a sort of horizontal ‘radial’ extension. This event is not older than the Late Pleistocene and possibly reflects the active stress field still dominating the entire study area.     

Water composition and minerals equilibria at the Syri i Kalter spring and in the Bistrica river (South Albania)

Syri i Kalter (“Blue Eye” in english) is the name of the largest spring of Albania, situated in the south of the country, not far from the town of Sarande. The spring is located near the tectonic contact between the Mesozoic-Paleogenic Mali i Gjiere carbonate sequence and the Terziary flysch units of the “Ionian Zone” of Albania. The discharge area is characterized by the presence of Triassic evaporites, mainly constituted by gypsum and anhydrite, associated with clay, limestones, dolomite and halite. The spring consists of several discharge points, yielding as a whole an average water flow of about 11 m³/s.