1,721,232 research outputs found
Application of the Wiener filter to magnetic profiling in the volcanic environment of Mt. Etna (Italy)
No full textThe frequency-domain Wiener filtering was applied to magnetic anomalies in the volcanic area of Mt. Etna. This filter, under suitable conditions (additive noise, linear processing and mean-square error criterion), can furnish an effective tool for discriminating the geologic feature of interest (the signal) from the noise. The filter was first tested with synthetic data. Afterwards it was applied to a magnetic profile carried out across the principal fault system of the Mt. Etna volcano, that hosted the dykes feeding both the 1989 and the 1991-93 eruptions. The magnetic anomalies linked to the volcanic section and those linked to the contact between the clay basement and the lava coverage show significant spectral overlap. Thus by estimating the power spectrum of the signal, obtained resolving the forward problem, a least-squares Wiener filter has been designed. In such context, it was possible to verify the effectiveness of Wiener filters, whereas traditional band-pass filtering proved inadequate. In fact, analysis of the noise showed that all the meaningful components of the observed magnetic field were resolved. The results put further constraints on location and geometry of the shallow plumbing system of Mt. Etna.JCR Journalope
Time dependent piezomagnetic fields in viscoelastic medium
No full textWe investigated time dependent piezomagnetic fields due to volcanic sources embedded in a
viscoelastic, homogeneous half-space. Especially in volcanic areas, the presence of inhomogeneous
materials and high temperatures produce a lower effective viscosity of the Earth’s
crust that calls for considering anelastic properties of the medium. Piezomagnetic properties
are carried by grains of titano-magnetite, which occupy only a small fraction of ordinary rock
volume and are supposed to be elastic, while the non-magnetic surrounding matrix is assumed
to be viscoelastic. From all the possible rheological models, we investigated two cases in which
the bulk modulus is purely elastic and the shear modulus relaxes as: (i) a Maxwell solid and
(ii) a standard linear solid (SLS). We applied the Correspondence Principle to the analytical
elastic solutions for pressurized spherical sources and dislocation sources in order to determine
the time dependent piezomagnetic fields in a viscoelastic medium. The piezomagnetic field
completely vanishes after the relaxation process for a Maxwell rheology, whereas it is found
to decrease over time and reach some finite offset value for a SLS rheology. These different
behaviours provide helpful hints in understanding the temporal evolution of piezomagnetic
anomalies in volcanic regions.Published536-5483.6. Fisica del vulcanismoJCR Journalreserve
Time variant analysis of geomagnetic signals describes the volcanic activity of Mt. Etna between early 2000 and late 2002
No full textMagmatic intrusion determined from self-potential and magnetic measurements at Mt:Etna. , 403-414.
No full textMagmatic intrusion determined from self-potential and magnetic measurements at Mt:Etna. , 403-414.
No full textMagmatic Gas Leakage at Mount Etna (Sicily, Italy): Relationships With the Volcano-Tectonic Structures, the Hydrological Pattern and the Eruptive Activity
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