Mt Etna volcano: modelling of ground deformation patterns of recent eruptions and considerations on the associated precursors

The study of the ground deformation associated with the recent eruptions of the Etna volcano (1981, 1989, 1991-93) furnished the opportunity to observe different behaviour relating to the eruptive activity, and suggested different feeding and penetration mechanisms inside the volcano edifice. In particular, the analytical modelling of geodetic data was applied to study the strain sources of these eruptions, by the application of single and multiple source-models, i.e. composed of two single sources. In particular, a single tensile dislocation was used to model the SE fracture associated with the 1989 eruption; a double tensile dislocation was adopted to interpret and model the deformation pattern of the 1981 eruption; a double source composed of a tensile dislocation (for the final eruptive fracture) and a depressuring body (for the deflation during the eruption course) was considered for the 1991-93 eruption. The results of this modelling show that, however, the final uprising system, i.e. the tensile mechanisms inside the volcano edifice, involved the same structure, oriented approximately NNW-SSE. This structure was activated by different eruption mechanisms with associated different deformation patterns during these three recent eruptions. A review of the methodologies applied and main results obtained in modelling of different sources and mechanisms is presented here. The analysis of the deformation data and the performed modelling evidence that the associated precursors can strongly change for the different eruptions. In addition, the implications both in terms of how the volcano works and in terms of ground deformation precursors are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.