Finite element simulation of freezing processes in soils

The finite element method, formulated for non-linear heat conduction, allows the solution of practically any ground freezing problem. Stabilization of wet soils by artificial freezing and freezing under roads induced by cold winter conditions are considered in this paper. Special features of the program used include parabolic isoparametric elements, a new time stepping scheme and an improved procedure for the estimation of thermal properties.     

Magma convection and mixing dynamics as a source of Ultra-Long-Period oscillations

Many volcanic eruptions are shortly preceded by injection of new magma into a pre-existing, shallow (<10 km) magma chamber, causing convection and mixing between the incoming and resident magmas. These processes may trigger dyke propagation and further magma rise, inducing long-term (days to months) volcano deformation, seismic swarms, gravity anomalies, and changes in the composition of volcanic plumes and fumaroles, eventually culminating in an eruption. Although new magma injection into shallow magma chambers can lead to hazardous event, such injection is still not systematically detected and recognized. Here, we present the results of numerical simulations of magma convection and mixing in geometrically complex magmatic systems, and describe the multiparametric dynamics associated with buoyant magma injection. Our results reveal unexpected pressure trends and pressure oscillations in the Ultra-Long-Period (ULP) range of minutes, related to the generation of discrete plumes of rising magma. Very long pressure oscillation wavelengths translate into comparably ULP ground displacements with amplitudes of order 10⁻⁴–10⁻² m. Thus, new magma injection into magma chambers beneath volcanoes can be revealed by ULP ground displacement measured at the surface.     

Numerical solution of the discontinuous-bottom Shallow-water Equations with hydrostatic pressure distribution at the step

Free-surface flows are usually modelled by means of the Shallow-water Equations: this system of hyperbolic equations exhibits a source term which is proportional to the product of the water depth by the bed slope, and which takes into account the effect of gravity onto fluid mass. Recently, much attention has been paid to the case in which bottom discontinuities are present in the physical domain to be represented: in this case, it is difficult to define the non-conservative product in the distributional sense. Here, the discontinuous-bottom Shallow-water Equations with hydrostatic pressure distribution at the bed step (Bernetti et al., 2006) are discussed in the context of the theory of Dal Maso et al. (1995) [9]; finally, a first-order numerical scheme is presented, which is consistent for regular solutions, and which is able to capture contact discontinuities at bottom steps. Numerous tests are presented to show the feasibility of the scheme and its ability to converge to the exact solution in the cases of smooth as well as discontinuous bed profiles.     

What do the orbital motions of the outer planets of the Solar System tell us about the Pioneer anomaly?

In this paper, we investigate the effects that an anomalous acceleration as that experienced by the Pioneer spacecraft after they passed the 20 AU threshold would induce on the orbital motions of the Solar System planets placed at heliocentric distances of 20 AU or larger as Uranus, Neptune and Pluto. It turns out that such an acceleration, with a magnitude of 8.74 × 10⁻¹⁰ m s⁻², would affect their orbits with secular and short-period signals large enough to be detected according to the latest published results by E.V. Pitjeva, even by considering errors up to 30 times larger than those released. The absence of such anomalous signatures in the latest data rules out the possibility that in the region 20–40 AU of the Solar System an anomalous force field inducing a constant and radial acceleration with those characteristics affects the motion of the major planets.     

The role of the NNW structural trend in the recent geodynamic evolution of north-eastern sicily and its volcanic implications in the etnean area

The seismic and eruptive events occurring in Eastern Sicily between 1978 and 1981 are analyzed with reference to the existence neoctectonic structures beginning with the Gulf of Patti earthquake (1978, Lower Tyrrhenian Basin). From this analysis, the geodynamic consistency of the movements developing along the NNW and NE trends becomes apparent. In particular, the relation between these two trends enables the authors to verify their previously elaborated deformation model for the Etnean area and to emphasize its coherence with the regional geodynamic context. Finally, the close connection is shown between the Etnean area and the NNW-SSE wrench zone breaking the Southern Calabro-Peloritan Arc.