Volcanic risk in the explosive Campi Flegrei (CF) caldera is extremely high, because of its location in a densely populated area about 15 km west of Naples inside the Campanian Plain. CF is renowned as a site of continual slow vertical movements. Since the last eruption in 1538, the caldera generally subsided until 1969 then uplift began in the early 1970s (about 1.5 m max), a further large uplift episode occurred from 1982 to 1984 (about 1.8 m max), and a few smaller uplift episodes occurred in 1989, 1994, 2000, and 2006. From 2006, CF is mostly uplifting. Ground deformation monitoring of CF started in 1905, when the Istituto Geografico Militare established a first leveling line from Naples to Serapeum; since then the leveling line has been much extended and now the leveling network consists of 350 altimetric benchmarks. Geodetic precise-traversing surveys-distance (EDM) and angular measurements were carried out from time to time, starting from June 1970. A Continuous Global Positioning System (CGPS) network began operating at the end of the 1990s. Ground displacement data from Synthetic Aperture Radar (SAR) Interferometry are available since 1992. Such an abundance of data has allowed detailed studies of the ground deformation time history. In particular, we have recently found that CF ground deformation, within data uncertainties, is always given by the sum of two "stationary contributions" at least since 1980. Large-scale deformation can be explained by a quasi-horizontal source, oriented NW/SE and mathematically represented by a pressurized finite thin triaxial ellipsoid (PTE) embedded in a layered medium at about 4 km; residual deformation not accounted for by PTE can be mathematically explained by a small (point) pressurized oblate spheroid about 2 km below the Solfatara fumarolic field. The location and geometry of the two sources are constant with the exception of volume changes (potency); potency time histories are somewhat similar but not identical. A long-standing controversy characterizes the interpretation of CF inflation and deflation phases, which are generally ascribed to fluid injections at the basis of the hydrothermal system or to shallow magma injections. As a matter of fact, all published models of both processes predict complex spatial and/or temporal patterns of CF ground deformation. We will give a review of our knowledge about CF ground deformation and present a new model of magma intrusion, which is consistent with the observed constancy of the ground deformation pattern.
What is behind Campi Flegrei inflations and deflations? Clues from 35 years of geodetic monitoring.
CRESCENTINI, Luca;AMORUSO, ANTONELLA
2016-01-01
Abstract
Volcanic risk in the explosive Campi Flegrei (CF) caldera is extremely high, because of its location in a densely populated area about 15 km west of Naples inside the Campanian Plain. CF is renowned as a site of continual slow vertical movements. Since the last eruption in 1538, the caldera generally subsided until 1969 then uplift began in the early 1970s (about 1.5 m max), a further large uplift episode occurred from 1982 to 1984 (about 1.8 m max), and a few smaller uplift episodes occurred in 1989, 1994, 2000, and 2006. From 2006, CF is mostly uplifting. Ground deformation monitoring of CF started in 1905, when the Istituto Geografico Militare established a first leveling line from Naples to Serapeum; since then the leveling line has been much extended and now the leveling network consists of 350 altimetric benchmarks. Geodetic precise-traversing surveys-distance (EDM) and angular measurements were carried out from time to time, starting from June 1970. A Continuous Global Positioning System (CGPS) network began operating at the end of the 1990s. Ground displacement data from Synthetic Aperture Radar (SAR) Interferometry are available since 1992. Such an abundance of data has allowed detailed studies of the ground deformation time history. In particular, we have recently found that CF ground deformation, within data uncertainties, is always given by the sum of two "stationary contributions" at least since 1980. Large-scale deformation can be explained by a quasi-horizontal source, oriented NW/SE and mathematically represented by a pressurized finite thin triaxial ellipsoid (PTE) embedded in a layered medium at about 4 km; residual deformation not accounted for by PTE can be mathematically explained by a small (point) pressurized oblate spheroid about 2 km below the Solfatara fumarolic field. The location and geometry of the two sources are constant with the exception of volume changes (potency); potency time histories are somewhat similar but not identical. A long-standing controversy characterizes the interpretation of CF inflation and deflation phases, which are generally ascribed to fluid injections at the basis of the hydrothermal system or to shallow magma injections. As a matter of fact, all published models of both processes predict complex spatial and/or temporal patterns of CF ground deformation. We will give a review of our knowledge about CF ground deformation and present a new model of magma intrusion, which is consistent with the observed constancy of the ground deformation pattern.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
