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Modélisation numérique des mouvements de flanc de l'Etna (Sicile, Italie) mis en évidence par interférométrie radar

Abstract : Recent interferometric studies have evidenced large scale motions affecting the southern and southeastern flank of Mount Etna. These studies are based on ascending interferograms and few ERS scenes. In our study, we analyse more than 600 hundreds SAR interferograms for both ascending and descending satellites passes, recorded between September 1992 and August 2000. Our study reveals that, since March 1996, displacements along several faults located on the eastern and southeastern flank of the edifice have occurred. Displacement rates slowly decreased and motions stopped in august 1998. Assuming that both ascending and descending interferograms are insensitive to the northward component of displacements, we computed vertical and eastward components of displacements. This shows that the Mascalucia-Trecastagni-Tremestieri (MTT) and the Ragalna faults were undergoing horizontal displacement, consistent with a displacement of the eastern flank of the volcano to the east, and that the anticlinal ridge at the southern base of the volcano was being uplifted. Moreover, our study reveals that some segments of the faults were active between January 1999 and November 2000. In both case, the onset of displacements was synchronous with explosive volcanic events in the summit area, showing a link between creep along the faults and volcanic activity. Previously proposed geodynamical models differ mainly on the location of the southern and southwestern boundary of the mobile sector. The proposed boundaries are located in the area where displacements have been evidenced by interferometry. We use a 3D mixed boundary elements method in order to constrain the southern and horizontal boundaries of the eastern and southern sector, as well as the stress field responsible for the observed motions. The measured displacements are consistent with the activation of 2 different decollements, and a stress field varying with depth. The uplift along the anticlinal ridge south of the volcano is consistent with the N-S regional compression acting on a north dipping decollement with a depth varying from 2.5 km to 5 km below sea level. This decollement could be inherited from the Maghrebo-Appenine Chain. The ESE sliding of the Eastern flank is related with a shallower decollement limited by the Pernicana-Provenzana fault to the North and by the MTT faults to the south. This decollement is located in the sedimentary basement a few hundred meters below sea level. The driving force of the eastward instability could be gravitational forces and a regional E-W extension. We have also determined that the magmatic forces related with magma injection in the rift zones are not the driving forces for the eastern flank. Nevertheless, displacements created by magmatic forces are consistent with displacements observed on the western flank of the volcano and it is likely that magmatic forces provided the trigger to flank displacements to the east and southeast.
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https://tel.archives-ouvertes.fr/tel-00008932
Contributor : Fabien Ranvier <>
Submitted on : Friday, April 1, 2005 - 10:19:44 PM
Last modification on : Friday, April 19, 2019 - 1:47:34 AM
Long-term archiving on: : Friday, April 2, 2010 - 9:17:44 PM

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  • HAL Id : tel-00008932, version 1

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Fabien Ranvier. Modélisation numérique des mouvements de flanc de l'Etna (Sicile, Italie) mis en évidence par interférométrie radar. Sciences de la Terre. Université Blaise Pascal - Clermont-Ferrand II, 2004. Français. ⟨tel-00008932⟩

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