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School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland
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- PublicationRestrictedAn integrated method to model volcanic processes and associated geophysical signals(2009)
; ; ; ; ; ; ; ; ;Vassalli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Longo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Montagna, C. P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;O'Brien, G. S.; School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland ;Bean, C. J.; School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland ;Bisconti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Papale, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; ; ; ; ; ; ; We present a numerical approach for modelling the complex sub-surface volcanic processes and associated geophysical signals. This method is based on the one-way coupling of the dynamics of a magmatic system and the response of the host rocks. The two systems are modelled independently, by two different numerical codes, that solve the equations of motion for the magmatic fluid and the equation of elasto-dynamics for wave propagation in the surrounding medium, respectively. Synthetic geophysical signals can be obtained and compared with those recorded by monitoring networks. The final aim is to understand how the complex physics of magma dynamics, coupled to its hosting medium, translates into geophysical data that can be measured and interpreted in order to understand sub-surface magma dynamics and forecast the short-term volcanic hazard. We applied this method to the Campi Flegrei volcanic system (southern Italy) and investigated the convection and mixing dynamics induced by the arrival of new CO2-rich magma into a hypothetical shallow magma chamber. The pressure waves originated by this system are propagated in the surrounding rocks, and the associated broad-band ground displacement and gravity anomalies are evaluated at the Earth’s surface.266 64 - PublicationRestrictedNumerical simulation of convection and mixing in magma chambers replenished with CO2-rich magma(2006)
; ; ; ; ;Longo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Vassalli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Papale, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Barsanti, M.; Dipartimento di Matematica Applicata, Universita` di Pisa, Pisa, Italy; ; ; Magma convection and mixing, and periodic refilling, commonly occur in magma chambers.We show here that the presence of CO2 in the refilling magma is a very efficient mean of inducing buoyant-driven plume rise and large scale convection. Numerical simulations performed with an appositely developed code for the transient 2D dynamics of multicomponent compressible to incompressible fluids reveal several features of the processes of plume rise, convection and mixing in magma chambers associated with chamber refilling. A parametric study on CO2 abundance in the refilling magma shows that progressively larger amounts of this volatile produce a shift from simple plume rise and spreading near the chamber top, to complex patterns of flow circulation and large scale vorticity and mixing. Lower chamber depth and lower magma viscosity largely enhance the efficiency of mixing and convection, favoring the formation of multiple vortexes migrating with time.257 28 - PublicationOpen AccessA numerical code for the simulation of magma-rocks dynamics(2009)
; ; ; ; ; ; ; ;Longo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Barsanti, M.; Dipartimento di Matematica Applicata "U. Dini", Università degli Studi di Pisa, Pisa, Italy ;Papale, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Vassalli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Montagna, C. P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Bisconti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Saccorotti, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; ; ; ; ; ; We present a numerical code for the simulation of the dynamics of compressible to incompressible, multicomponent ows, based on the _nite element algorithm by Hauke & Hughes (1998). Balance equations for mass, momentum, energy and composition are solved with space-time Galerkin least-squares and discontinuity-capturing stabilizing techniques. The code is used to study the dynamics of convection and mixing in magmatic systems such as replenishment of magma chambers and volcanic conduits, and it reveals the occurrence of previously not described processes. The uid-structure interaction of fully coupled magma-rock dynamics is being implemented by using the deforming-spatial domain method by Tezduyar (2006), that intrinsecally includes moving meshes.513 170 - PublicationRestrictedNon-Newtonian rheology of crystal-bearing magmas and implications for magma ascent dynamics(2007)
; ; ; ; ; ; ;Caricchi, L.; Department of Earth Sciences, ETH Zurich ;Burlini, L.; Department of Earth Sciences, ETH Zurich ;Ulmer, P.; Department of Earth Sciences, ETH Zurich ;Gerya, T.; Department of Earth Sciences, ETH Zurich ;Vassalli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Papale, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; ; ; ; ; The eruptive dynamics of volcanic systems are largely controlled by the viscosity of deforming magma. Here we report the results of a series of high-temperature, high-pressure experiments at conditions relevant for volcanic conduits (250 MPa confining pressure and temperature between 500 °C and 900 °C) that were undertaken to investigate the rheology of magma with crystal fractions varying between 0.5 and 0.8 (50 to 80 wt.%) at different strain-rate conditions. The experiments demonstrate that the presence of crystals increases the relative viscosity (ratio between the viscosity of the mixture and the viscosity of the melt phase) of magmas and additionally induces a decrease of the relative viscosity with increasing strain-rate (shear thinning, non-Newtonian behavior). The experimental results, combined with existing data at low crystal fractions (0–0.3), were used to develop a semi-empirical parameterization that describes the variations of relative viscosity for crystal fractions between 0 and 0.8 and accounts for the complex non-Newtonian rheology of crystal-bearing magmas. The new parameterization, included into numerical models simulating the magma ascent dynamics, reveals that strain-rate-dependent rheology significantly modifies the dynamic behavior inside volcanic conduits, particularly affecting the magma fragmentation conditions.137 932 - 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