Since 1993 geodetic data obtained by different techniques (GPS, EDM, SAR, leveling) detected a consistent inflation of the Mount Etna volcano. The inflation, culminated with the 1998-2001 strong explosive activity from summit craters and recent 2001 and 2002 flank eruptions, may be interpreted by magma ascent and re-filling of the volcanic plumbing system and reservoirs. Our purpose is to model the 1993-97 GPS and EDM data by pressurized sources simulating the magma reservoir using a 3D Finite Element modeling coupled to a Neighbourhood Algorithm inversion. The power of this technique, if compared with analytical inversions, is that sources can be placed in complex media (heterogeneous, with topography, inelastic, etc.) so that the inversion result is not influenced by the usual approximations of elastic, homogeneous half-space. We model the inflation by a deep volcanic source, considered as point source. The source intensity is given by its stress tensor, identifying an ellipsoidal pressure source. The FE model of Mt. Etna is characterized by a regular mesh below the volcanic edifice, and by arbitrarily distorted brick elements elsewhere. The potential point sources are contained in a cubic volume located below the summit craters, between 4 km and 8 km b.s.l.. For each potential source we compute the deformation and elongation at GPS and EDM observation points. The solution is a weighted combination of displacements (one for each stress component) computed for each of the potential sources. The best source parameters search is performed by the Neighbourhood Algorithm inversion technique. Good results from synthetic tests and previous inversions with only GPS data confirm the robustness of the method. We consider four classes of models characterized by: i) homogeneous medium and flat free surface; ii) homogeneous medium with topography of Mt. Etna; iii) heterogeneous medium with flat free surface; iv) heterogeneous medium with topography. Results from data inversion show evidence for a vertically elongated body. This result is a robust feature of the inversions, since it is common to models with/without topography and with/without rigidity contrasts. Differences in the location and dimension of the ellipsoid are due to the presence of the rigidity contrasts and topography. Solutions are compared also with those derived by inversions of analytical forward models in the homogeneous medium with flat free surface, showing good agreement.

Numerical inversion of 1993-97 deformation data at Mount Etna (Italy)

TRASATTI, ELISA;BONAFEDE, MAURIZIO
2005

Abstract

Since 1993 geodetic data obtained by different techniques (GPS, EDM, SAR, leveling) detected a consistent inflation of the Mount Etna volcano. The inflation, culminated with the 1998-2001 strong explosive activity from summit craters and recent 2001 and 2002 flank eruptions, may be interpreted by magma ascent and re-filling of the volcanic plumbing system and reservoirs. Our purpose is to model the 1993-97 GPS and EDM data by pressurized sources simulating the magma reservoir using a 3D Finite Element modeling coupled to a Neighbourhood Algorithm inversion. The power of this technique, if compared with analytical inversions, is that sources can be placed in complex media (heterogeneous, with topography, inelastic, etc.) so that the inversion result is not influenced by the usual approximations of elastic, homogeneous half-space. We model the inflation by a deep volcanic source, considered as point source. The source intensity is given by its stress tensor, identifying an ellipsoidal pressure source. The FE model of Mt. Etna is characterized by a regular mesh below the volcanic edifice, and by arbitrarily distorted brick elements elsewhere. The potential point sources are contained in a cubic volume located below the summit craters, between 4 km and 8 km b.s.l.. For each potential source we compute the deformation and elongation at GPS and EDM observation points. The solution is a weighted combination of displacements (one for each stress component) computed for each of the potential sources. The best source parameters search is performed by the Neighbourhood Algorithm inversion technique. Good results from synthetic tests and previous inversions with only GPS data confirm the robustness of the method. We consider four classes of models characterized by: i) homogeneous medium and flat free surface; ii) homogeneous medium with topography of Mt. Etna; iii) heterogeneous medium with flat free surface; iv) heterogeneous medium with topography. Results from data inversion show evidence for a vertically elongated body. This result is a robust feature of the inversions, since it is common to models with/without topography and with/without rigidity contrasts. Differences in the location and dimension of the ellipsoid are due to the presence of the rigidity contrasts and topography. Solutions are compared also with those derived by inversions of analytical forward models in the homogeneous medium with flat free surface, showing good agreement.
EOS Transactions American Geophysical Union
V21D-
0652
EOS
TRASATTI E.; PIANA AGOSTINETTI N.; CIANETTI S.; GIUNCHI C.; BONACCORSO S.; BONAFEDE M.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/120037
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