About the Symmetry of the Upscaled Equivalent Transmissivity Tensor

This paper provides a proof of the symmetry of the equivalent transmissivity tensor computed with a method based on the solution of the balance equation at the fine scale with integrated finite differences. The basic hypotheses are that the balance equation is solved on a block assigning Dirichlet boundary conditions that vary linearly with the space coordinates and the equivalent transmissivity tensor is computed as the linear tensor relating average flux and hydraulic gradient.     

Quantitative methods for estimating flood fatalities: towards the introduction of loss-of-life estimation in the assessment of flood risk

Risk, including flood risk, can be defined as ??the combination of the probability of an event and its consequences??. Assessing and managing the risk from flooding should explicitly include the estimation of impacts to people. Extensive research is currently ongoing looking at both quantitative and qualitative approaches for assessing flood impacts on people. Although there is some literature available on such approaches, examples of methodological and routinely applications of these methodologies as part of flood risk assessments are rare. This paper focuses on quantitative approaches for estimating impacts of flooding to people, notably on methods for assessing fatality numbers associated with flooding. Three methods for assessing losses of life are discussed in detail. The methods discussed here constitute the forefront of research in Canada, UK and The Netherlands. These methods provide an assessment of the physical consequences of flooding on people and can be used to introduce the impacts to people as quantitative metric for the assessment of flood risk. In this paper, the three methodologies are discussed and applied in a UK case study reproducing the 1953 East Coast flood event. This study aims to provide a comprehensive comparison on both the reliability and the applicability of the methods. We analyse possible added values on using of these methods in systematic analyses, aiming to provide guidelines for applying these methods for flood fatality risk assessment.     

Lunar capture trajectories and homoclinic connections through isomorphic mapping

Analysis and design of low-energy transfers to the Moon has been a subject of great interest for many decades. This paper is concerned with a topological study of such transfers, with emphasis to trajectories that allow performing lunar capture and those that exhibit homoclinic connections, in the context of the circular restricted three-body problem. A fundamental theorem stated by Conley locates capture trajectories in the phase space and can be condensed in a sentence: “if a crossing asymptotic orbit exists then near any such there is a capture orbit”. In this work this fundamental theoretical assertion is used together with an original cylindrical isomorphic mapping of the phase space associated with the third body dynamics. For a given energy level, the stable and unstable invariant manifolds of the periodic Lyapunov orbit around the collinear interior Lagrange point are computed and represented in cylindrical coordinates as tubes that emanate from the transformed periodic orbit. These tubes exhibit complex geometrical features. Their intersections correspond to homoclinic orbits and determine the topological separation of long-term lunar capture orbits from short-duration capture trajectories. The isomorphic mapping is proven to allow a deep insight on the chaotic motion that characterizes the dynamics of the circular restricted three-body, and suggests an interesting interpretation, and together corroboration, of Conley’s assertion on the topological location of lunar capture orbits. Moreover, an alternative three-dimensional representation of the phase space is profitably employed to identify convenient lunar periodic orbits that can be entered with modest propellant consumption, starting from the Lyapunov orbit.     

Reinterpretation of Tractus Fossae region as an asymmetric rift system on Mars

The Tractus Fossae region of Mars is a wide area dominated by grabens, normal faults and pit crater chains. In this work, based on previous studies on the area and the new interpretation of topographic data and morphological units based on images as a geologic framework we present a new insight on the origin of the graben structures as well as on the processes associated with the formation of the volcanic features. Here we propose a new model for this region, on the basis of new measurements of graben extension and geological interpretations, together with a reinterpretation of the stratigraphy and the geologic history of the area. Finally, it is postulated that this region underwent a tectonic regime analog to an asymmetric rift system on Earth.     

Effects of different boundary conditions on the simulation of groundwater flow in a multi-layered coastal aquifer system (Taranto Gulf,southern Italy)

The evaluation of the accuracy or reasonableness of numerical models of groundwater flow is a complex task, due to the uncertainties in hydrodynamic properties and boundary conditions and the scarcity of good-quality field data. To assess model reliability, different calibration techniques are joined to evaluate the effects of different kinds of boundary conditions on the groundwater flow in a coastal multi-layered aquifer in southern Italy. In particular, both direct and indirect approaches for inverse modeling were joined through the calibration of one of the most uncertain parameters, namely the hydraulic conductivity of the karst deep hydrostratigraphic unit. The methodology proposed here, and applied to a real case study, confirmed that the selection of boundary conditions is among the most critical and difficult aspects of the characterization of a groundwater system for conceptual analysis or numerical simulation. The practical tests conducted in this study show that incorrect specification of boundary conditions prevents an acceptable match between the model response to the hydraulic stresses and the behavior of the natural system. Such effects have a negative impact on the applicability of numerical modeling to simulate groundwater dynamics in complex hydrogeological situations. This is particularly important for management of the aquifer system investigated in this work, which represents the only available freshwater resource of the study area, and is threatened by overexploitation and saltwater intrusion.     

Experimental constraints on the origin and evolution of mildly alkalic basalts from the Kerguelen Archipelago, Southeast Indian Ocean

This experimental study examines the role of clinopyroxene fractionation on major element trends and alkalinity variations in mildly alkalic basalts from the Kerguelen Archipelago, Southeast Indian Ocean. Equilibrium crystallization experiments were carried out on a natural basalt (MgO=5 wt.%, alkalinity index=0.10) over a range of pressures (0–1.43 GPa) and water contents (nominally dry to hydrous, 1.2 wt.% H₂O) under relatively oxidizing conditions (Δlog FMQ=+1 to +2) at 0 GPa and relatively reducing conditions (Δlog FMQ=0 to –2) at all higher pressures. The hydrous experiments at 0.93 GPa closely reproduce most of the compositional variations in the 24–25 Ma mildly alkalic lavas from the archipelago, which supports a major role for high-Al clinopyroxene fractionation (5–9 wt.% Al₂O₃) at pressures corresponding to the base of the Northern Kerguelen Plateau (15–20 km). However, clinopyroxene fractionation at depth fails to produce important changes in the alkalinity of the residual melts. The transition from tholeiitic to mildly alkalic basalts on the Kerguelen Archipelago thus reflects primarily changes in melting conditions (lower extents of partial melting at higher pressures), which is related to crustal and lithospheric thickening as distance from the Southeast Indian Ridge increased over time from 43 to 24 Ma.