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Cassioli, A.
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Cassioli, A.
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- PublicationRestrictedMagma convection and mixing dynamics as a source of Ultra-Long-Period oscillations(2012)
; ; ; ; ; ; ; ; ;Longo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Papale, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Vassalli, M.; School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland ;Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Montagna, C. P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Cassioli, A.; Dipartimento di Sistemi e Informatica, Università di Firenze, Firenze, Italy ;Giudice, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Boschi, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione AC, Roma, Italia; ; ; ; ; ; ; 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.608 32 - PublicationRestrictedA finite element Galerkin/least-squares method for computation of multicomponent compressible–incompressible flows(2012-08-30)
; ; ; ; ;Longo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Barsanti, M.; Dipartimento di Matematica Applicata, University of Pisa, Pisa, Italy ;Cassioli, A.; Dipartimento di Sistemi e Informatica, University of Florence, Florence, Italy ;Papale, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; ; ; The space–time Galerkin/least-squares finite element method with discontinuity capturing (ST-GLSDC), developed by Hughes and collaborators [Shakib et al. A new finite element formulation for computational fluid dynamics: X. The compressible Euler and Navier–Stokes equations. Comput Methods Appl Mech Eng 1991;89:141–219], allows to study both compressible and incompressible single-fluid one-component flows. It is effective in the stabilization of the numerical solution without introducing excessive overdiffusion. In this work the development by Hauke and Hughes [A comparative study of different sets of variables for solving compressible and incompressible flows. Comput Methods Appl Mech Eng 1998;153:1–44] to pressure primitive variables is extended to single-fluid multicomponent compressible and incompressible flows of gas–liquid mixtures at local mechanical and chemical equilibrium. The stabilized algorithm is implemented in a parallel C++ library, which is tested on several benchmarks. The solution of the system of equations for the conservation of mass of each component, and of momentum and energy of the global mixture, requires the introduction of mass fractions as primitive variables to describe mixture composition. The weak formulation, the stabilization parameters, and the time-marching algorithm are rewritten in terms of the expanded set of variables, keeping similarity with the formulation in pressure variables.392 45