ABSTRACT The structure of a volcanic edifice depends on composition, volume of erupted magma, and... more ABSTRACT The structure of a volcanic edifice depends on composition, volume of erupted magma, and mechanism of eruption. In particular, pressure variations with depth due to density variations of the volcanic rocks are crucial for magma degassing processes as well as buoyancy mechanisms. In this paper, we analyze the effects of three different pressure profiles with depth on the probability of occurrence of simulated eruptive events. We describe the dynamics of magma ascent by means of a time dependent Self-Organized-Criticality field, which controls the opening of crack networks through which discrete magma batches are allowed to rise. We find a characteristic power-law behavior for the number of eruptions with erupted volume in all considered cases. As concerns the probability of occurrence of an eruptive event with a given percentage of gas losses, we find that extreme events, i.e., events with the lowest percentage of gas losses, are more likely to occur if a step function is used to describe the relationship between rock density and depth.
... Chapter 1 The volcanological history of the volcanoes of Naples: a review Roberto Scandone*, ... more ... Chapter 1 The volcanological history of the volcanoes of Naples: a review Roberto Scandone*, Lisetta Giacomelli and Francesca Fattori Speranza Dipartimento di Fisica ... Di Vito, MA, Isaia, R., Orsi, G.. Southon, J.. de Vita, S., D'Antonio, M., Pappalardo, L., Piochi, M., 1999. ...
ABSTRACT Campi Flegrei is a densely inhabited volcanic area within a caldera, 12-14 km in diamete... more ABSTRACT Campi Flegrei is a densely inhabited volcanic area within a caldera, 12-14 km in diameter, immedi-ately west of Naples, Italy. In 1970-1972 and in 1982-1984, Campi Flegrei experienced considerable ground surface deformation producing a bulge about 3.5 m high at its peak. In the two inflation episodes the point of maximum uplift did not change, coinciding with the caldera center, about which the displacements exhibited radial symmetry. The 1982-1984 uplift was accompanied by considerable seismic activity. Gravity changes have been interpreted as reflecting the occurrence of a subvertical magmatic intrusion. Volcanological, petrological, and geophysical data point to the existence of a shallow magma chamber just beneath the center of the caldera. We assume that the observed surface displacements are the response of an essentially elastic medium to a pressure increase in the magma chamber. Static deformation is calculated by using a finite-element method, assuming axial symmetry around a vertical axis through the caldera center. The role played by various components of the model, geometry, bound-ary conditions, elastic properties, is analyzed. It is shown that models assuming uniform elasticity are inadequate. Therefore the major volcanotectonic features as well as the influence of temperature and pressure on the elastic properties are taken into account. The results of various more complex models are presented. It is suggested that a progressively fractured zone, whose size and shape depend also on the possible occurrence of magmatic intrusions, may explain the observed surface displacements and the other data collected at Campi Flegrei. It is suggested that the 1970-1972 uplift was possibly accompanied by larger-scale changes in the stress field.
ABSTRACT The structure of a volcanic edifice depends on composition, volume of erupted magma, and... more ABSTRACT The structure of a volcanic edifice depends on composition, volume of erupted magma, and mechanism of eruption. In particular, pressure variations with depth due to density variations of the volcanic rocks are crucial for magma degassing processes as well as buoyancy mechanisms. In this paper, we analyze the effects of three different pressure profiles with depth on the probability of occurrence of simulated eruptive events. We describe the dynamics of magma ascent by means of a time dependent Self-Organized-Criticality field, which controls the opening of crack networks through which discrete magma batches are allowed to rise. We find a characteristic power-law behavior for the number of eruptions with erupted volume in all considered cases. As concerns the probability of occurrence of an eruptive event with a given percentage of gas losses, we find that extreme events, i.e., events with the lowest percentage of gas losses, are more likely to occur if a step function is used to describe the relationship between rock density and depth.
... Chapter 1 The volcanological history of the volcanoes of Naples: a review Roberto Scandone*, ... more ... Chapter 1 The volcanological history of the volcanoes of Naples: a review Roberto Scandone*, Lisetta Giacomelli and Francesca Fattori Speranza Dipartimento di Fisica ... Di Vito, MA, Isaia, R., Orsi, G.. Southon, J.. de Vita, S., D'Antonio, M., Pappalardo, L., Piochi, M., 1999. ...
ABSTRACT Campi Flegrei is a densely inhabited volcanic area within a caldera, 12-14 km in diamete... more ABSTRACT Campi Flegrei is a densely inhabited volcanic area within a caldera, 12-14 km in diameter, immedi-ately west of Naples, Italy. In 1970-1972 and in 1982-1984, Campi Flegrei experienced considerable ground surface deformation producing a bulge about 3.5 m high at its peak. In the two inflation episodes the point of maximum uplift did not change, coinciding with the caldera center, about which the displacements exhibited radial symmetry. The 1982-1984 uplift was accompanied by considerable seismic activity. Gravity changes have been interpreted as reflecting the occurrence of a subvertical magmatic intrusion. Volcanological, petrological, and geophysical data point to the existence of a shallow magma chamber just beneath the center of the caldera. We assume that the observed surface displacements are the response of an essentially elastic medium to a pressure increase in the magma chamber. Static deformation is calculated by using a finite-element method, assuming axial symmetry around a vertical axis through the caldera center. The role played by various components of the model, geometry, bound-ary conditions, elastic properties, is analyzed. It is shown that models assuming uniform elasticity are inadequate. Therefore the major volcanotectonic features as well as the influence of temperature and pressure on the elastic properties are taken into account. The results of various more complex models are presented. It is suggested that a progressively fractured zone, whose size and shape depend also on the possible occurrence of magmatic intrusions, may explain the observed surface displacements and the other data collected at Campi Flegrei. It is suggested that the 1970-1972 uplift was possibly accompanied by larger-scale changes in the stress field.
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