Search

Abstract: Major results of post-intrusive GPS monitoring of the 5 months encompassing and following the onset of 2002–03 Mt. Etna eruption are presented and discussed here. The overall ground deformation pattern is characterized by a time-dependent relaxation function. We evaluated two different parametrizations of relaxation functions, each one linked to a different relaxation process: i) viscoelastic relaxation and ii) after-slip mechanism. The former indicated that the process occurred within a weak layer characterized by viscosity values ranging between 7.1 · 1014 Pa s and 1.3 · 1015 Pa s. The latter evidenced that frictional processes occurred beneath a layer of velocity-strengthening having a thickness with values ranging between 0.4 km and 1.7 km. Either model may explain the observed time-dependent deformation, both from the statistical point of view and the comparison with geologic and seismic information. Although we are unable to favour one model rather than the other, these results indicate that the mechanism, responsible for the observed post-intrusive deformation, occurs within a sliding “zone” located inside the clayey sedimentary basement. [Copyright &y& Elsevier]

Abstract: Combined GPS measurements and radar interferometry (InSAR) have been applied at Mt. Etna to study the ground deformation affecting the volcano both over the long- (1993–2000) and short-term (1997–1998 and 1998–2000). The aim was to better understand the dynamics of the volcano during the magma-recharging phase following the 1991–93 eruption. Since 1993, InSAR and GPS data indicate that Mt. Etna has undergone an inflation. A deep intrusion was detected by InSAR, on the western flank of the volcano, between March and May 1997. In the following months, this intrusion rose up leading to a seismic swarm occurring in January 1998 in the western sector. This now shallow intrusion is confirmed by GPS data. From 1998 to 2000, a general deflation affecting the upper part of the volcano was detected. Over the whole study period, a continuous eastward to south-eastward motion of the eastern sector of the volcano was also evidenced. The analytical inversions of GPS data inferred a plane dipping about 12°ESE, located beneath the eastern flank of the volcano at a depth of 1.4 km b.s.l. The movement along this plane is able to reproduce the observed south-eastward motion of a sector bounded northward by the Pernicana fault, westward by the North–East Rift and the South Rift, and southward by the Mascalucia–Tremestieri–Trecastagni fault system. InSAR data have validated this model. [Copyright &y& Elsevier]

ive volcanoes characterized by open conduit conditions generate sonic and infrasonic signals, whose investigation provides useful information for both monitoring purposes and studying the dynamics of explosive processes. In this work, we discuss the automatic procedures implemented for a real-time application to the data acquired by a permanent network of five infrasound stations running at Mt. Etna volcano. The infrasound signals at Mt. Etna consist in amplitude transients, called infrasound events. The adopted procedure uses a multi-algorithm approach for event detection, counting, characterization and location. It is designed for an efficient and accurate processing of infrasound records provided by single-site and array stations. Moreover, the source mechanism of these events can be investigated off-line or in near real-time by using three different models: (1) Strombolian bubble; (2) resonating conduit and (3) Helmholtz resonator. The infrasound waveforms allow us to choose the most suitable model, to get quantitative information about the source and to follow the time evolution of the source parameters. [ABSTRACT FROM AUTHOR]